diff --git a/mojo/public/dart/third_party/string_scanner/.gitignore b/mojo/public/dart/third_party/string_scanner/.gitignore
new file mode 100644
index 0000000..7dbf035
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/.gitignore
@@ -0,0 +1,15 @@
+# Don’t commit the following directories created by pub.
+.buildlog
+.pub/
+build/
+packages
+.packages
+
+# Or the files created by dart2js.
+*.dart.js
+*.js_
+*.js.deps
+*.js.map
+
+# Include when developing application packages.
+pubspec.lock
\ No newline at end of file
diff --git a/mojo/public/dart/third_party/string_scanner/.test_config b/mojo/public/dart/third_party/string_scanner/.test_config
new file mode 100644
index 0000000..412fc5c
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/.test_config
@@ -0,0 +1,3 @@
+{
+  "test_package": true
+}
\ No newline at end of file
diff --git a/mojo/public/dart/third_party/string_scanner/CHANGELOG.md b/mojo/public/dart/third_party/string_scanner/CHANGELOG.md
new file mode 100644
index 0000000..23f911c
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/CHANGELOG.md
@@ -0,0 +1,70 @@
+## 0.1.4
+
+* Add `new SpanScanner.eager()` for creating a `SpanScanner` that eagerly
+  computes its current line and column numbers.
+
+## 0.1.3+2
+
+* Fix `LineScanner`'s handling of carriage returns to match that of
+  `SpanScanner`.
+
+## 0.1.3+1
+
+* Fixed the homepage URL.
+
+## 0.1.3
+
+* Add an optional `endState` argument to `SpanScanner.spanFrom`.
+
+## 0.1.2
+
+* Add `StringScanner.substring`, which returns a substring of the source string.
+
+## 0.1.1
+
+* Declare `SpanScanner`'s exposed `SourceSpan`s and `SourceLocation`s to be
+  `FileSpan`s and `FileLocation`s. They always were underneath, but callers may
+  now rely on it.
+
+* Add `SpanScanner.location`, which returns the scanner's current
+  `SourceLocation`.
+
+## 0.1.0
+
+* Switch from `source_maps`' `Span` class to `source_span`'s `SourceSpan` class.
+
+* `new StringScanner()`'s `sourceUrl` parameter is now named to make it clear
+  that it can be safely `null`.
+
+* `new StringScannerException()` takes different arguments in a different order
+  to match `SpanFormatException`.
+
+* `StringScannerException.string` has been renamed to
+  `StringScannerException.source` to match the `FormatException` interface.
+
+## 0.0.3
+
+* Make `StringScannerException` inherit from source_map's
+  [`SpanFormatException`][].
+
+[SpanFormatException]: (http://www.dartdocs.org/documentation/source_maps/0.9.2/index.html#source_maps/source_maps.SpanFormatException)
+
+## 0.0.2
+
+* `new StringScanner()` now takes an optional `sourceUrl` argument that provides
+  the URL of the source file. This is used for error reporting.
+
+* Add `StringScanner.readChar()` and `StringScanner.peekChar()` methods for
+  doing character-by-character scanning.
+
+* Scanners now throw `StringScannerException`s which provide more detailed
+  access to information about the errors that were thrown and can provide
+  terminal-colored messages.
+
+* Add a `LineScanner` subclass of `StringScanner` that automatically tracks line
+  and column information of the text being scanned.
+
+* Add a `SpanScanner` subclass of `LineScanner` that exposes matched ranges as
+  [source map][] `Span` objects.
+
+[source_map]: http://pub.dartlang.org/packages/source_maps
diff --git a/mojo/public/dart/third_party/string_scanner/LICENSE b/mojo/public/dart/third_party/string_scanner/LICENSE
new file mode 100644
index 0000000..5c60afe
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/LICENSE
@@ -0,0 +1,26 @@
+Copyright 2014, the Dart project authors. All rights reserved.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+    * Neither the name of Google Inc. nor the names of its
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/mojo/public/dart/third_party/string_scanner/README.md b/mojo/public/dart/third_party/string_scanner/README.md
new file mode 100644
index 0000000..90660fc
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/README.md
@@ -0,0 +1,37 @@
+This package exposes a `StringScanner` type that makes it easy to parse a string
+using a series of `Pattern`s. For example:
+
+```dart
+import 'dart:math';
+
+import 'package:string_scanner/string_scanner.dart';
+
+num parseNumber(String source) {
+  // Scan a number ("1", "1.5", "-3").
+  var scanner = new StringScanner(source);
+
+  // [Scanner.scan] tries to consume a [Pattern] and returns whether or not it
+  // succeeded. It will move the scan pointer past the end of the pattern.
+  var negative = scanner.scan("-");
+
+  // [Scanner.expect] consumes a [Pattern] and throws a [FormatError] if it
+  // fails. Like [Scanner.scan], it will move the scan pointer forward.
+  scanner.expect(new RegExp(r"\d+"));
+
+  // [Scanner.lastMatch] holds the [MatchData] for the most recent call to
+  // [Scanner.scan], [Scanner.expect], or [Scanner.matches].
+  var number = int.parse(scanner.lastMatch[0]);
+
+  if (scanner.scan(".")) {
+    scanner.expect(new RegExp(r"\d+"));
+    var decimal = scanner.lastMatch[0];
+    number += int.parse(decimal) / math.pow(10, decimal.length);
+  }
+
+  // [Scanner.expectDone] will throw a [FormatError] if there's any input that
+  // hasn't yet been consumed.
+  scanner.expectDone();
+
+  return (negative ? -1 : 1) * number;
+}
+```
diff --git a/mojo/public/dart/third_party/string_scanner/codereview.settings b/mojo/public/dart/third_party/string_scanner/codereview.settings
new file mode 100644
index 0000000..31c557f
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/codereview.settings
@@ -0,0 +1,3 @@
+CODE_REVIEW_SERVER: http://codereview.chromium.org/
+VIEW_VC: https://github.com/dart-lang/string_scanner/commit/
+CC_LIST: reviews@dartlang.org
\ No newline at end of file
diff --git a/mojo/public/dart/third_party/string_scanner/lib/src/eager_span_scanner.dart b/mojo/public/dart/third_party/string_scanner/lib/src/eager_span_scanner.dart
new file mode 100644
index 0000000..3fae5cc
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/lib/src/eager_span_scanner.dart
@@ -0,0 +1,115 @@
+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.eager_span_scanner;
+
+import 'package:charcode/ascii.dart';
+
+import 'line_scanner.dart';
+import 'span_scanner.dart';
+
+// TODO(nweiz): Currently this duplicates code in line_scanner.dart. Once
+// sdk#23770 is fully complete, we should move the shared code into a mixin.
+
+/// A regular expression matching newlines across platforms.
+final _newlineRegExp = new RegExp(r"\r\n?|\n");
+
+/// A [SpanScanner] that tracks the line and column eagerly, like [LineScanner].
+class EagerSpanScanner extends SpanScanner {
+  int get line => _line;
+  int _line = 0;
+
+  int get column => _column;
+  int _column = 0;
+
+  LineScannerState get state =>
+      new _EagerSpanScannerState(this, position, line, column);
+
+  bool get _betweenCRLF => peekChar(-1) == $cr && peekChar() == $lf;
+
+  set state(LineScannerState state) {
+    if (state is! _EagerSpanScannerState ||
+        !identical((state as _EagerSpanScannerState)._scanner, this)) {
+      throw new ArgumentError("The given LineScannerState was not returned by "
+          "this LineScanner.");
+    }
+
+    super.position = state.position;
+    _line = state.line;
+    _column = state.column;
+  }
+
+  set position(int newPosition) {
+    var oldPosition = position;
+    super.position = newPosition;
+
+    if (newPosition > oldPosition) {
+      var newlines = _newlinesIn(string.substring(oldPosition, newPosition));
+      _line += newlines.length;
+      if (newlines.isEmpty) {
+        _column += newPosition - oldPosition;
+      } else {
+        _column = newPosition - newlines.last.end;
+      }
+    } else {
+      var newlines = _newlinesIn(string.substring(newPosition, oldPosition));
+      if (_betweenCRLF) newlines.removeLast();
+
+      _line -= newlines.length;
+      if (newlines.isEmpty) {
+        _column -= oldPosition - newPosition;
+      } else {
+        _column = newPosition -
+            string.lastIndexOf(_newlineRegExp, newPosition) - 1;
+      }
+    }
+  }
+
+  EagerSpanScanner(String string, {sourceUrl, int position})
+      : super(string, sourceUrl: sourceUrl, position: position);
+
+  int readChar() {
+    var char = super.readChar();
+    if (char == $lf || (char == $cr && peekChar() != $lf)) {
+      _line += 1;
+      _column = 0;
+    } else {
+      _column += 1;
+    }
+    return char;
+  }
+
+  bool scan(Pattern pattern) {
+    if (!super.scan(pattern)) return false;
+
+    var newlines = _newlinesIn(lastMatch[0]);
+    _line += newlines.length;
+    if (newlines.isEmpty) {
+      _column += lastMatch[0].length;
+    } else {
+      _column = lastMatch[0].length - newlines.last.end;
+    }
+
+    return true;
+  }
+
+  /// Returns a list of [Match]es describing all the newlines in [text], which
+  /// is assumed to end at [position].
+  List<Match> _newlinesIn(String text) {
+    var newlines = _newlineRegExp.allMatches(text).toList();
+    if (_betweenCRLF) newlines.removeLast();
+    return newlines;
+  }
+}
+
+/// A class representing the state of an [EagerSpanScanner].
+class _EagerSpanScannerState implements LineScannerState {
+  final EagerSpanScanner _scanner;
+  final int position;
+  final int line;
+  final int column;
+
+  _EagerSpanScannerState(this._scanner, this.position, this.line, this.column);
+}
+
diff --git a/mojo/public/dart/third_party/string_scanner/lib/src/exception.dart b/mojo/public/dart/third_party/string_scanner/lib/src/exception.dart
new file mode 100644
index 0000000..50177d6
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/lib/src/exception.dart
@@ -0,0 +1,20 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.exception;
+
+import 'package:source_span/source_span.dart';
+
+/// An exception thrown by a [StringScanner] that failed to parse a string.
+class StringScannerException extends SourceSpanFormatException {
+  String get source => super.source;
+
+  /// The URL of the source file being parsed.
+  ///
+  /// This may be `null`, indicating that the source URL is unknown.
+  Uri get sourceUrl => span.sourceUrl;
+
+  StringScannerException(String message, SourceSpan span, String source)
+      : super(message, span, source);
+}
diff --git a/mojo/public/dart/third_party/string_scanner/lib/src/line_scanner.dart b/mojo/public/dart/third_party/string_scanner/lib/src/line_scanner.dart
new file mode 100644
index 0000000..66d7575
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/lib/src/line_scanner.dart
@@ -0,0 +1,127 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.line_scanner;
+
+import 'package:charcode/ascii.dart';
+
+import 'string_scanner.dart';
+
+// Note that much of this code is duplicated in eager_span_scanner.dart.
+
+/// A regular expression matching newlines across platforms.
+final _newlineRegExp = new RegExp(r"\r\n?|\n");
+
+/// A subclass of [StringScanner] that tracks line and column information.
+class LineScanner extends StringScanner {
+  /// The scanner's current (zero-based) line number.
+  int get line => _line;
+  int _line = 0;
+
+  /// The scanner's current (zero-based) column number.
+  int get column => _column;
+  int _column = 0;
+
+  /// The scanner's state, including line and column information.
+  ///
+  /// This can be used to efficiently save and restore the state of the scanner
+  /// when backtracking. A given [LineScannerState] is only valid for the
+  /// [LineScanner] that created it.
+  LineScannerState get state =>
+      new LineScannerState._(this, position, line, column);
+
+  /// Whether the current position is between a CR character and an LF
+  /// charactet.
+  bool get _betweenCRLF => peekChar(-1) == $cr && peekChar() == $lf;
+
+  set state(LineScannerState state) {
+    if (!identical(state._scanner, this)) {
+      throw new ArgumentError("The given LineScannerState was not returned by "
+          "this LineScanner.");
+    }
+
+    super.position = state.position;
+    _line = state.line;
+    _column = state.column;
+  }
+
+  set position(int newPosition) {
+    var oldPosition = position;
+    super.position = newPosition;
+
+    if (newPosition > oldPosition) {
+      var newlines = _newlinesIn(string.substring(oldPosition, newPosition));
+      _line += newlines.length;
+      if (newlines.isEmpty) {
+        _column += newPosition - oldPosition;
+      } else {
+        _column = newPosition - newlines.last.end;
+      }
+    } else {
+      var newlines = _newlinesIn(string.substring(newPosition, oldPosition));
+      if (_betweenCRLF) newlines.removeLast();
+
+      _line -= newlines.length;
+      if (newlines.isEmpty) {
+        _column -= oldPosition - newPosition;
+      } else {
+        _column = newPosition -
+            string.lastIndexOf(_newlineRegExp, newPosition) - 1;
+      }
+    }
+  }
+
+  LineScanner(String string, {sourceUrl, int position})
+      : super(string, sourceUrl: sourceUrl, position: position);
+
+  int readChar() {
+    var char = super.readChar();
+    if (char == $lf || (char == $cr && peekChar() != $lf)) {
+      _line += 1;
+      _column = 0;
+    } else {
+      _column += 1;
+    }
+    return char;
+  }
+
+  bool scan(Pattern pattern) {
+    if (!super.scan(pattern)) return false;
+
+    var newlines = _newlinesIn(lastMatch[0]);
+    _line += newlines.length;
+    if (newlines.isEmpty) {
+      _column += lastMatch[0].length;
+    } else {
+      _column = lastMatch[0].length - newlines.last.end;
+    }
+
+    return true;
+  }
+
+  /// Returns a list of [Match]es describing all the newlines in [text], which
+  /// is assumed to end at [position].
+  List<Match> _newlinesIn(String text) {
+    var newlines = _newlineRegExp.allMatches(text).toList();
+    if (_betweenCRLF) newlines.removeLast();
+    return newlines;
+  }
+}
+
+/// A class representing the state of a [LineScanner].
+class LineScannerState {
+  /// The [LineScanner] that created this.
+  final LineScanner _scanner;
+
+  /// The position of the scanner in this state.
+  final int position;
+
+  /// The zero-based line number of the scanner in this state.
+  final int line;
+
+  /// The zero-based column number of the scanner in this state.
+  final int column;
+
+  LineScannerState._(this._scanner, this.position, this.line, this.column);
+}
diff --git a/mojo/public/dart/third_party/string_scanner/lib/src/span_scanner.dart b/mojo/public/dart/third_party/string_scanner/lib/src/span_scanner.dart
new file mode 100644
index 0000000..ebe230d
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/lib/src/span_scanner.dart
@@ -0,0 +1,115 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.span_scanner;
+
+import 'package:source_span/source_span.dart';
+
+import 'eager_span_scanner.dart';
+import 'exception.dart';
+import 'line_scanner.dart';
+import 'string_scanner.dart';
+import 'utils.dart';
+
+/// A subclass of [LineScanner] that exposes matched ranges as source map
+/// [Span]s.
+class SpanScanner extends StringScanner implements LineScanner {
+  /// The source of the scanner.
+  ///
+  /// This caches line break information and is used to generate [Span]s.
+  final SourceFile _sourceFile;
+
+  int get line => _sourceFile.getLine(position);
+  int get column => _sourceFile.getColumn(position);
+
+  LineScannerState get state => new _SpanScannerState(this, position);
+
+  set state(LineScannerState state) {
+    if (state is! _SpanScannerState ||
+        !identical((state as _SpanScannerState)._scanner, this)) {
+      throw new ArgumentError("The given LineScannerState was not returned by "
+          "this LineScanner.");
+    }
+
+    this.position = state.position;
+  }
+
+  /// The [FileSpan] for [lastMatch].
+  ///
+  /// This is the span for the entire match. There's no way to get spans for
+  /// subgroups since [Match] exposes no information about their positions.
+  FileSpan get lastSpan => _lastSpan;
+  FileSpan _lastSpan;
+
+  /// The current location of the scanner.
+  FileLocation get location => _sourceFile.location(position);
+
+  /// Returns an empty span at the current location.
+  FileSpan get emptySpan => location.pointSpan();
+
+  /// Creates a new [SpanScanner] that starts scanning from [position].
+  ///
+  /// [sourceUrl] is used as [SourceLocation.sourceUrl] for the returned
+  /// [FileSpan]s as well as for error reporting. It can be a [String], a
+  /// [Uri], or `null`.
+  SpanScanner(String string, {sourceUrl, int position})
+      : _sourceFile = new SourceFile(string, url: sourceUrl),
+        super(string, sourceUrl: sourceUrl, position: position);
+
+  /// Creates a new [SpanScanner] that eagerly computes line and column numbers.
+  ///
+  /// In general [new SpanScanner] will be more efficient, since it avoids extra
+  /// computation on every scan. However, eager scanning can be useful for
+  /// situations where the normal course of parsing frequently involves
+  /// accessing the current line and column numbers.
+  ///
+  /// Note that *only* the `line` and `column` fields on the `SpanScanner`
+  /// itself and its `LineScannerState` are eagerly computed. To limit their
+  /// memory footprint, returned spans and locations will still lazily compute
+  /// their line and column numbers.
+  factory SpanScanner.eager(String string, {sourceUrl, int position}) =
+      EagerSpanScanner;
+
+  /// Creates a [FileSpan] representing the source range between [startState]
+  /// and the current position.
+  FileSpan spanFrom(LineScannerState startState, [LineScannerState endState]) {
+    var endPosition = endState == null ? position : endState.position;
+    return _sourceFile.span(startState.position, endPosition);
+  }
+
+  bool matches(Pattern pattern) {
+    if (!super.matches(pattern)) {
+      _lastSpan = null;
+      return false;
+    }
+
+    _lastSpan = _sourceFile.span(position, lastMatch.end);
+    return true;
+  }
+
+  void error(String message, {Match match, int position, int length}) {
+    validateErrorArgs(string, match, position, length);
+
+    if (match == null && position == null && length == null) match = lastMatch;
+    if (position == null) {
+      position = match == null ? this.position : match.start;
+    }
+    if (length == null) length = match == null ? 1 : match.end - match.start;
+
+    var span = _sourceFile.span(position, position + length);
+    throw new StringScannerException(message, span, string);
+  }
+}
+
+/// A class representing the state of a [SpanScanner].
+class _SpanScannerState implements LineScannerState {
+  /// The [SpanScanner] that created this.
+  final SpanScanner _scanner;
+
+  final int position;
+  int get line => _scanner._sourceFile.getLine(position);
+  int get column => _scanner._sourceFile.getColumn(position);
+
+  _SpanScannerState(this._scanner, this.position);
+}
diff --git a/mojo/public/dart/third_party/string_scanner/lib/src/string_scanner.dart b/mojo/public/dart/third_party/string_scanner/lib/src/string_scanner.dart
new file mode 100644
index 0000000..d9c1c2f
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/lib/src/string_scanner.dart
@@ -0,0 +1,176 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.string_scanner;
+
+import 'package:source_span/source_span.dart';
+
+import 'exception.dart';
+import 'utils.dart';
+
+/// When compiled to JS, forward slashes are always escaped in [RegExp.pattern].
+///
+/// See issue 17998.
+final _slashAutoEscape = new RegExp("/").pattern == "\\/";
+
+/// A class that scans through a string using [Pattern]s.
+class StringScanner {
+  /// The URL of the source of the string being scanned.
+  ///
+  /// This is used for error reporting. It may be `null`, indicating that the
+  /// source URL is unknown or unavailable.
+  final Uri sourceUrl;
+
+  /// The string being scanned through.
+  final String string;
+
+  /// The current position of the scanner in the string, in characters.
+  int get position => _position;
+  set position(int position) {
+    if (position < 0 || position > string.length) {
+      throw new ArgumentError("Invalid position $position");
+    }
+
+    _position = position;
+  }
+  int _position = 0;
+
+  /// The data about the previous match made by the scanner.
+  ///
+  /// If the last match failed, this will be `null`.
+  Match get lastMatch => _lastMatch;
+  Match _lastMatch;
+
+  /// The portion of the string that hasn't yet been scanned.
+  String get rest => string.substring(position);
+
+  /// Whether the scanner has completely consumed [string].
+  bool get isDone => position == string.length;
+
+  /// Creates a new [StringScanner] that starts scanning from [position].
+  ///
+  /// [position] defaults to 0, the beginning of the string. [sourceUrl] is the
+  /// URL of the source of the string being scanned, if available. It can be
+  /// a [String], a [Uri], or `null`.
+  StringScanner(this.string, {sourceUrl, int position})
+      : sourceUrl = sourceUrl is String ? Uri.parse(sourceUrl) : sourceUrl {
+    if (position != null) this.position = position;
+  }
+
+  /// Consumes a single character and returns its character code.
+  ///
+  /// This throws a [FormatException] if the string has been fully consumed. It
+  /// doesn't affect [lastMatch].
+  int readChar() {
+    if (isDone) _fail("more input");
+    return string.codeUnitAt(_position++);
+  }
+
+  /// Returns the character code of the character [offset] away from [position].
+  ///
+  /// [offset] defaults to zero, and may be negative to inspect already-consumed
+  /// characters.
+  ///
+  /// This returns `null` if [offset] points outside the string. It doesn't
+  /// affect [lastMatch].
+  int peekChar([int offset]) {
+    if (offset == null) offset = 0;
+    var index = position + offset;
+    if (index < 0 || index >= string.length) return null;
+    return string.codeUnitAt(index);
+  }
+
+  /// If [pattern] matches at the current position of the string, scans forward
+  /// until the end of the match.
+  ///
+  /// Returns whether or not [pattern] matched.
+  bool scan(Pattern pattern) {
+    var success = matches(pattern);
+    if (success) _position = _lastMatch.end;
+    return success;
+  }
+
+  /// If [pattern] matches at the current position of the string, scans forward
+  /// until the end of the match.
+  ///
+  /// If [pattern] did not match, throws a [FormatException] describing the
+  /// position of the failure. [name] is used in this error as the expected name
+  /// of the pattern being matched; if it's `null`, the pattern itself is used
+  /// instead.
+  void expect(Pattern pattern, {String name}) {
+    if (scan(pattern)) return;
+
+    if (name == null) {
+      if (pattern is RegExp) {
+        var source = pattern.pattern;
+        if (!_slashAutoEscape) source = source.replaceAll("/", "\\/");
+        name = "/$source/";
+      } else {
+        name =
+            pattern.toString().replaceAll("\\", "\\\\").replaceAll('"', '\\"');
+        name = '"$name"';
+      }
+    }
+    _fail(name);
+  }
+
+  /// If the string has not been fully consumed, this throws a
+  /// [FormatException].
+  void expectDone() {
+    if (isDone) return;
+    _fail("no more input");
+  }
+
+  /// Returns whether or not [pattern] matches at the current position of the
+  /// string.
+  ///
+  /// This doesn't move the scan pointer forward.
+  bool matches(Pattern pattern) {
+    _lastMatch = pattern.matchAsPrefix(string, position);
+    return _lastMatch != null;
+  }
+
+  /// Returns the substring of [string] between [start] and [end].
+  ///
+  /// Unlike [String.substring], [end] defaults to [position] rather than the
+  /// end of the string.
+  String substring(int start, [int end]) {
+    if (end == null) end = position;
+    return string.substring(start, end);
+  }
+
+  /// Throws a [FormatException] with [message] as well as a detailed
+  /// description of the location of the error in the string.
+  ///
+  /// [match] is the match information for the span of the string with which the
+  /// error is associated. This should be a match returned by this scanner's
+  /// [lastMatch] property. By default, the error is associated with the last
+  /// match.
+  ///
+  /// If [position] and/or [length] are passed, they are used as the error span
+  /// instead. If only [length] is passed, [position] defaults to the current
+  /// position; if only [position] is passed, [length] defaults to 1.
+  ///
+  /// It's an error to pass [match] at the same time as [position] or [length].
+  void error(String message, {Match match, int position, int length}) {
+    validateErrorArgs(string, match, position, length);
+
+    if (match == null && position == null && length == null) match = lastMatch;
+    if (position == null) {
+      position = match == null ? this.position : match.start;
+    }
+    if (length == null) length = match == null ? 1 : match.end - match.start;
+
+    var sourceFile = new SourceFile(string, url: sourceUrl);
+    var span = sourceFile.span(position, position + length);
+    throw new StringScannerException(message, span, string);
+  }
+
+  // TODO(nweiz): Make this handle long lines more gracefully.
+  /// Throws a [FormatException] describing that [name] is expected at the
+  /// current position in the string.
+  void _fail(String name) {
+    error("expected $name.", position: this.position, length: 0);
+  }
+}
diff --git a/mojo/public/dart/third_party/string_scanner/lib/src/utils.dart b/mojo/public/dart/third_party/string_scanner/lib/src/utils.dart
new file mode 100644
index 0000000..107c4c5
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/lib/src/utils.dart
@@ -0,0 +1,30 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.utils;
+
+/// Validates the arguments passed to [StringScanner.error].
+void validateErrorArgs(String string, Match match, int position, int length) {
+  if (match != null && (position != null || length != null)) {
+    throw new ArgumentError("Can't pass both match and position/length.");
+  }
+
+  if (position != null) {
+    if (position < 0) {
+      throw new RangeError("position must be greater than or equal to 0.");
+    } else if (position > string.length) {
+      throw new RangeError("position must be less than or equal to the "
+          "string length.");
+    }
+  }
+
+  if (length != null && length < 0) {
+    throw new RangeError("length must be greater than or equal to 0.");
+  }
+
+  if (position != null && length != null && position + length > string.length) {
+    throw new RangeError("position plus length must not go beyond the end of "
+        "the string.");
+  }
+}
diff --git a/mojo/public/dart/third_party/string_scanner/lib/string_scanner.dart b/mojo/public/dart/third_party/string_scanner/lib/string_scanner.dart
new file mode 100644
index 0000000..be294f4
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/lib/string_scanner.dart
@@ -0,0 +1,11 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// A library for parsing strings using a sequence of patterns.
+library string_scanner;
+
+export 'src/exception.dart';
+export 'src/line_scanner.dart';
+export 'src/span_scanner.dart';
+export 'src/string_scanner.dart';
diff --git a/mojo/public/dart/third_party/string_scanner/pubspec.yaml b/mojo/public/dart/third_party/string_scanner/pubspec.yaml
new file mode 100644
index 0000000..35b3fe0
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/pubspec.yaml
@@ -0,0 +1,14 @@
+name: string_scanner
+version: 0.1.4
+author: "Dart Team <misc@dartlang.org>"
+homepage: https://github.com/dart-lang/string_scanner
+description: >
+  A class for parsing strings using a sequence of patterns.
+dependencies:
+  charcode: "^1.1.0"
+  path: "^1.2.0"
+  source_span: "^1.0.0"
+dev_dependencies:
+  test: ">=0.12.0 <0.13.0"
+environment:
+  sdk: ">=1.8.0 <2.0.0"
diff --git a/mojo/public/dart/third_party/string_scanner/test/error_test.dart b/mojo/public/dart/third_party/string_scanner/test/error_test.dart
new file mode 100644
index 0000000..9c485e5
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/test/error_test.dart
@@ -0,0 +1,149 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.error_test;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:test/test.dart';
+
+import 'utils.dart';
+
+void main() {
+  test('defaults to the last match', () {
+    var scanner = new StringScanner('foo bar baz');
+    scanner.expect('foo ');
+    scanner.expect('bar');
+    expect(() => scanner.error('oh no!'), throwsStringScannerException('bar'));
+  });
+
+  group("with match", () {
+    test('supports an earlier match', () {
+      var scanner = new StringScanner('foo bar baz');
+      scanner.expect('foo ');
+      var match = scanner.lastMatch;
+      scanner.expect('bar');
+      expect(() => scanner.error('oh no!', match: match),
+          throwsStringScannerException('foo '));
+    });
+
+    test('supports a match on a previous line', () {
+      var scanner =
+          new StringScanner('foo bar baz\ndo re mi\nearth fire water');
+      scanner.expect('foo bar baz\ndo ');
+      scanner.expect('re');
+      var match = scanner.lastMatch;
+      scanner.expect(' mi\nearth ');
+      expect(() => scanner.error('oh no!', match: match),
+          throwsStringScannerException('re'));
+    });
+
+    test('supports a multiline match', () {
+      var scanner =
+          new StringScanner('foo bar baz\ndo re mi\nearth fire water');
+      scanner.expect('foo bar ');
+      scanner.expect('baz\ndo');
+      var match = scanner.lastMatch;
+      scanner.expect(' re mi');
+      expect(() => scanner.error('oh no!', match: match),
+          throwsStringScannerException('baz\ndo'));
+    });
+
+    test('supports a match after position', () {
+      var scanner = new StringScanner('foo bar baz');
+      scanner.expect('foo ');
+      scanner.expect('bar');
+      var match = scanner.lastMatch;
+      scanner.position = 0;
+      expect(() => scanner.error('oh no!', match: match),
+          throwsStringScannerException('bar'));
+    });
+  });
+
+  group("with position and/or length", () {
+    test('defaults to length 1', () {
+      var scanner = new StringScanner('foo bar baz');
+      scanner.expect('foo ');
+      expect(() => scanner.error('oh no!', position: 1),
+          throwsStringScannerException('o'));
+    });
+
+    test('defaults to the current position', () {
+      var scanner = new StringScanner('foo bar baz');
+      scanner.expect('foo ');
+      expect(() => scanner.error('oh no!', length: 3),
+          throwsStringScannerException('bar'));
+    });
+
+    test('supports an earlier position', () {
+      var scanner = new StringScanner('foo bar baz');
+      scanner.expect('foo ');
+      expect(() => scanner.error('oh no!', position: 1, length: 2),
+          throwsStringScannerException('oo'));
+    });
+
+    test('supports a position on a previous line', () {
+      var scanner =
+          new StringScanner('foo bar baz\ndo re mi\nearth fire water');
+      scanner.expect('foo bar baz\ndo re mi\nearth');
+      expect(() => scanner.error('oh no!', position: 15, length: 2),
+          throwsStringScannerException('re'));
+    });
+
+    test('supports a multiline length', () {
+      var scanner =
+          new StringScanner('foo bar baz\ndo re mi\nearth fire water');
+      scanner.expect('foo bar baz\ndo re mi\nearth');
+      expect(() => scanner.error('oh no!', position: 8, length: 8),
+          throwsStringScannerException('baz\ndo r'));
+    });
+
+    test('supports a position after the current one', () {
+      var scanner = new StringScanner('foo bar baz');
+      expect(() => scanner.error('oh no!', position: 4, length: 3),
+          throwsStringScannerException('bar'));
+    });
+
+    test('supports a length of zero', () {
+      var scanner = new StringScanner('foo bar baz');
+      expect(() => scanner.error('oh no!', position: 4, length: 0),
+          throwsStringScannerException(''));
+    });
+  });
+
+  group("argument errors", () {
+    var scanner;
+    setUp(() {
+      scanner = new StringScanner('foo bar baz');
+      scanner.scan('foo');
+    });
+
+    test("if match is passed with position", () {
+      expect(
+          () => scanner.error("oh no!", match: scanner.lastMatch, position: 1),
+          throwsArgumentError);
+    });
+
+    test("if match is passed with length", () {
+      expect(() => scanner.error("oh no!", match: scanner.lastMatch, length: 1),
+          throwsArgumentError);
+    });
+
+    test("if position is negative", () {
+      expect(() => scanner.error("oh no!", position: -1), throwsArgumentError);
+    });
+
+    test("if position is outside the string", () {
+      expect(() => scanner.error("oh no!", position: 100), throwsArgumentError);
+    });
+
+    test("if position + length is outside the string", () {
+      expect(() => scanner.error("oh no!", position: 7, length: 7),
+          throwsArgumentError);
+    });
+
+    test("if length is negative", () {
+      expect(() => scanner.error("oh no!", length: -1), throwsArgumentError);
+    });
+  });
+}
diff --git a/mojo/public/dart/third_party/string_scanner/test/line_scanner_test.dart b/mojo/public/dart/third_party/string_scanner/test/line_scanner_test.dart
new file mode 100644
index 0000000..68e5c38
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/test/line_scanner_test.dart
@@ -0,0 +1,136 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.line_scanner_test;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:test/test.dart';
+
+void main() {
+  var scanner;
+  setUp(() {
+    scanner = new LineScanner('foo\nbar\r\nbaz');
+  });
+
+  test('begins with line and column 0', () {
+    expect(scanner.line, equals(0));
+    expect(scanner.column, equals(0));
+  });
+
+  group("scan()", () {
+    test("consuming no newlines increases the column but not the line", () {
+      scanner.scan('foo');
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(3));
+    });
+
+    test("consuming a newline resets the column and increases the line", () {
+      scanner.expect('foo\nba');
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(2));
+    });
+
+    test("consuming multiple newlines resets the column and increases the line",
+        () {
+      scanner.expect('foo\nbar\r\nb');
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(1));
+    });
+
+    test("consuming halfway through a CR LF doesn't count as a line", () {
+      scanner.expect('foo\nbar\r');
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(4));
+
+      scanner.expect('\nb');
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(1));
+    });
+  });
+
+  group("readChar()", () {
+    test("on a non-newline character increases the column but not the line",
+        () {
+      scanner.readChar();
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(1));
+    });
+
+    test("consuming a newline resets the column and increases the line", () {
+      scanner.expect('foo');
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(3));
+
+      scanner.readChar();
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(0));
+    });
+
+    test("consuming halfway through a CR LF doesn't count as a line", () {
+      scanner.expect('foo\nbar');
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(3));
+
+      scanner.readChar();
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(4));
+
+      scanner.readChar();
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(0));
+    });
+  });
+
+  group("position=", () {
+    test("forward through newlines sets the line and column", () {
+      scanner.position = 10; // "foo\nbar\r\nb"
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(1));
+    });
+
+    test("forward through no newlines sets the column", () {
+      scanner.position = 2; // "fo"
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(2));
+    });
+
+    test("backward through newlines sets the line and column", () {
+      scanner.scan("foo\nbar\r\nbaz");
+      scanner.position = 2; // "fo"
+      expect(scanner.line, equals(0));
+      expect(scanner.column, equals(2));
+    });
+
+    test("backward through no newlines sets the column", () {
+      scanner.scan("foo\nbar\r\nbaz");
+      scanner.position = 10; // "foo\nbar\r\nb"
+      expect(scanner.line, equals(2));
+      expect(scanner.column, equals(1));
+    });
+
+    test("forward halfway through a CR LF doesn't count as a line", () {
+      scanner.position = 8; // "foo\nbar\r"
+      expect(scanner.line, equals(1));
+      expect(scanner.column, equals(4));
+    });
+  });
+
+  test("state= restores the line, column, and position", () {
+    scanner.scan('foo\nb');
+    var state = scanner.state;
+
+    scanner.scan('ar\nba');
+    scanner.state = state;
+    expect(scanner.rest, equals('ar\r\nbaz'));
+    expect(scanner.line, equals(1));
+    expect(scanner.column, equals(1));
+  });
+
+  test("state= rejects a foreign state", () {
+    scanner.scan('foo\nb');
+
+    expect(() => new LineScanner(scanner.string).state = scanner.state,
+        throwsArgumentError);
+  });
+}
diff --git a/mojo/public/dart/third_party/string_scanner/test/span_scanner_test.dart b/mojo/public/dart/third_party/string_scanner/test/span_scanner_test.dart
new file mode 100644
index 0000000..114bff7
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/test/span_scanner_test.dart
@@ -0,0 +1,70 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.span_scanner_test;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:test/test.dart';
+
+void main() {
+  testForImplementation("lazy", () {
+    return new SpanScanner('foo\nbar\nbaz', sourceUrl: 'source');
+  });
+
+  testForImplementation("eager", () {
+    return new SpanScanner.eager('foo\nbar\nbaz', sourceUrl: 'source');
+  });
+}
+
+void testForImplementation(String name, SpanScanner create()) {
+  group("for a $name scanner", () {
+    var scanner;
+    setUp(() => scanner = create());
+
+    test("tracks the span for the last match", () {
+      scanner.scan('fo');
+      scanner.scan('o\nba');
+
+      var span = scanner.lastSpan;
+      expect(span.start.offset, equals(2));
+      expect(span.start.line, equals(0));
+      expect(span.start.column, equals(2));
+      expect(span.start.sourceUrl, equals(Uri.parse('source')));
+
+      expect(span.end.offset, equals(6));
+      expect(span.end.line, equals(1));
+      expect(span.end.column, equals(2));
+      expect(span.start.sourceUrl, equals(Uri.parse('source')));
+
+      expect(span.text, equals('o\nba'));
+    });
+
+    test(".spanFrom() returns a span from a previous state", () {
+      scanner.scan('fo');
+      var state = scanner.state;
+      scanner.scan('o\nba');
+      scanner.scan('r\nba');
+
+      var span = scanner.spanFrom(state);
+      expect(span.text, equals('o\nbar\nba'));
+    });
+
+    test(".emptySpan returns an empty span at the current location", () {
+      scanner.scan('foo\nba');
+
+      var span = scanner.emptySpan;
+      expect(span.start.offset, equals(6));
+      expect(span.start.line, equals(1));
+      expect(span.start.column, equals(2));
+      expect(span.start.sourceUrl, equals(Uri.parse('source')));
+
+      expect(span.end.offset, equals(6));
+      expect(span.end.line, equals(1));
+      expect(span.end.column, equals(2));
+      expect(span.start.sourceUrl, equals(Uri.parse('source')));
+
+      expect(span.text, equals(''));
+    });
+  });
+}
diff --git a/mojo/public/dart/third_party/string_scanner/test/string_scanner_test.dart b/mojo/public/dart/third_party/string_scanner/test/string_scanner_test.dart
new file mode 100644
index 0000000..c8e43a5
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/test/string_scanner_test.dart
@@ -0,0 +1,337 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.string_scanner_test;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('with an empty string', () {
+    var scanner;
+    setUp(() {
+      scanner = new StringScanner('');
+    });
+
+    test('is done', () {
+      expect(scanner.isDone, isTrue);
+      expect(scanner.expectDone, isNot(throwsFormatException));
+    });
+
+    test('rest is empty', () {
+      expect(scanner.rest, isEmpty);
+    });
+
+    test('lastMatch is null', () {
+      expect(scanner.lastMatch, isNull);
+    });
+
+    test('position is zero', () {
+      expect(scanner.position, equals(0));
+    });
+
+    test("readChar fails and doesn't change the state", () {
+      expect(scanner.readChar, throwsFormatException);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test("peekChar returns null and doesn't change the state", () {
+      expect(scanner.peekChar(), isNull);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test("scan returns false and doesn't change the state", () {
+      expect(scanner.scan(new RegExp('.')), isFalse);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test("expect throws a FormatException and doesn't change the state", () {
+      expect(() => scanner.expect(new RegExp('.')), throwsFormatException);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test("matches returns false and doesn't change the state", () {
+      expect(scanner.matches(new RegExp('.')), isFalse);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test("substring returns the empty string", () {
+      expect(scanner.substring(0), isEmpty);
+    });
+
+    test('setting position to 1 throws an ArgumentError', () {
+      expect(() {
+        scanner.position = 1;
+      }, throwsArgumentError);
+    });
+
+    test('setting position to -1 throws an ArgumentError', () {
+      expect(() {
+        scanner.position = -1;
+      }, throwsArgumentError);
+    });
+  });
+
+  group('at the beginning of a string', () {
+    var scanner;
+    setUp(() {
+      scanner = new StringScanner('foo bar');
+    });
+
+    test('is not done', () {
+      expect(scanner.isDone, isFalse);
+      expect(scanner.expectDone, throwsFormatException);
+    });
+
+    test('rest is the whole string', () {
+      expect(scanner.rest, equals('foo bar'));
+    });
+
+    test('lastMatch is null', () {
+      expect(scanner.lastMatch, isNull);
+    });
+
+    test('position is zero', () {
+      expect(scanner.position, equals(0));
+    });
+
+    test('readChar returns the first character and moves forward', () {
+      expect(scanner.readChar(), equals(0x66));
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(1));
+    });
+
+    test('peekChar returns the first character', () {
+      expect(scanner.peekChar(), equals(0x66));
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test('peekChar with an argument returns the nth character', () {
+      expect(scanner.peekChar(4), equals(0x62));
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+    });
+
+    test("a matching scan returns true and changes the state", () {
+      expect(scanner.scan(new RegExp('f(..)')), isTrue);
+      expect(scanner.lastMatch[1], equals('oo'));
+      expect(scanner.position, equals(3));
+      expect(scanner.rest, equals(' bar'));
+    });
+
+    test("a non-matching scan returns false and sets lastMatch to null", () {
+      expect(scanner.matches(new RegExp('f(..)')), isTrue);
+      expect(scanner.lastMatch, isNotNull);
+
+      expect(scanner.scan(new RegExp('b(..)')), isFalse);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+      expect(scanner.rest, equals('foo bar'));
+    });
+
+    test("a matching expect changes the state", () {
+      scanner.expect(new RegExp('f(..)'));
+      expect(scanner.lastMatch[1], equals('oo'));
+      expect(scanner.position, equals(3));
+      expect(scanner.rest, equals(' bar'));
+    });
+
+    test("a non-matching expect throws a FormatException and sets lastMatch to "
+        "null", () {
+      expect(scanner.matches(new RegExp('f(..)')), isTrue);
+      expect(scanner.lastMatch, isNotNull);
+
+      expect(() => scanner.expect(new RegExp('b(..)')), throwsFormatException);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+      expect(scanner.rest, equals('foo bar'));
+    });
+
+    test("a matching matches returns true and only changes lastMatch", () {
+      expect(scanner.matches(new RegExp('f(..)')), isTrue);
+      expect(scanner.lastMatch[1], equals('oo'));
+      expect(scanner.position, equals(0));
+      expect(scanner.rest, equals('foo bar'));
+    });
+
+    test("a non-matching matches returns false and doesn't change the state",
+        () {
+      expect(scanner.matches(new RegExp('b(..)')), isFalse);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(0));
+      expect(scanner.rest, equals('foo bar'));
+    });
+
+    test("substring from the beginning returns the empty string", () {
+      expect(scanner.substring(0), isEmpty);
+    });
+
+    test("substring with a custom end returns the substring", () {
+      expect(scanner.substring(0, 3), equals('foo'));
+    });
+
+    test("substring with the string length returns the whole string", () {
+      expect(scanner.substring(0, 7), equals('foo bar'));
+    });
+
+    test('setting position to 1 moves the cursor forward', () {
+      scanner.position = 1;
+      expect(scanner.position, equals(1));
+      expect(scanner.rest, equals('oo bar'));
+
+      expect(scanner.scan(new RegExp('oo.')), isTrue);
+      expect(scanner.lastMatch[0], equals('oo '));
+      expect(scanner.position, equals(4));
+      expect(scanner.rest, equals('bar'));
+    });
+
+    test('setting position beyond the string throws an ArgumentError', () {
+      expect(() {
+        scanner.position = 8;
+      }, throwsArgumentError);
+    });
+
+    test('setting position to -1 throws an ArgumentError', () {
+      expect(() {
+        scanner.position = -1;
+      }, throwsArgumentError);
+    });
+
+    test('scan accepts any Pattern', () {
+      expect(scanner.scan('foo'), isTrue);
+      expect(scanner.lastMatch[0], equals('foo'));
+      expect(scanner.position, equals(3));
+      expect(scanner.rest, equals(' bar'));
+    });
+
+    test('scans multiple times', () {
+      expect(scanner.scan(new RegExp('f(..)')), isTrue);
+      expect(scanner.lastMatch[1], equals('oo'));
+      expect(scanner.position, equals(3));
+      expect(scanner.rest, equals(' bar'));
+
+      expect(scanner.scan(new RegExp(' b(..)')), isTrue);
+      expect(scanner.lastMatch[1], equals('ar'));
+      expect(scanner.position, equals(7));
+      expect(scanner.rest, equals(''));
+      expect(scanner.isDone, isTrue);
+      expect(scanner.expectDone, isNot(throwsFormatException));
+    });
+  });
+
+  group('at the end of a string', () {
+    var scanner;
+    setUp(() {
+      scanner = new StringScanner('foo bar');
+      expect(scanner.scan('foo bar'), isTrue);
+    });
+
+    test('is done', () {
+      expect(scanner.isDone, isTrue);
+      expect(scanner.expectDone, isNot(throwsFormatException));
+    });
+
+    test('rest is empty', () {
+      expect(scanner.rest, isEmpty);
+    });
+
+    test('position is zero', () {
+      expect(scanner.position, equals(7));
+    });
+
+    test("readChar fails and doesn't change the state", () {
+      expect(scanner.readChar, throwsFormatException);
+      expect(scanner.lastMatch, isNotNull);
+      expect(scanner.position, equals(7));
+    });
+
+    test("peekChar returns null and doesn't change the state", () {
+      expect(scanner.peekChar(), isNull);
+      expect(scanner.lastMatch, isNotNull);
+      expect(scanner.position, equals(7));
+    });
+
+    test("scan returns false and sets lastMatch to null", () {
+      expect(scanner.scan(new RegExp('.')), isFalse);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(7));
+    });
+
+    test("expect throws a FormatException and sets lastMatch to null", () {
+      expect(() => scanner.expect(new RegExp('.')), throwsFormatException);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(7));
+    });
+
+    test("matches returns false sets lastMatch to null", () {
+      expect(scanner.matches(new RegExp('.')), isFalse);
+      expect(scanner.lastMatch, isNull);
+      expect(scanner.position, equals(7));
+    });
+
+    test("substring from the beginning returns the whole string", () {
+      expect(scanner.substring(0), equals('foo bar'));
+    });
+
+    test("substring with a custom start returns a substring from there", () {
+      expect(scanner.substring(4), equals('bar'));
+    });
+
+    test("substring with a custom start and end returns that substring", () {
+      expect(scanner.substring(3, 5), equals(' b'));
+    });
+
+    test('setting position to 1 moves the cursor backward', () {
+      scanner.position = 1;
+      expect(scanner.position, equals(1));
+      expect(scanner.rest, equals('oo bar'));
+
+      expect(scanner.scan(new RegExp('oo.')), isTrue);
+      expect(scanner.lastMatch[0], equals('oo '));
+      expect(scanner.position, equals(4));
+      expect(scanner.rest, equals('bar'));
+    });
+
+    test('setting position beyond the string throws an ArgumentError', () {
+      expect(() {
+        scanner.position = 8;
+      }, throwsArgumentError);
+    });
+
+    test('setting position to -1 throws an ArgumentError', () {
+      expect(() {
+        scanner.position = -1;
+      }, throwsArgumentError);
+    });
+  });
+
+  group('a scanner constructed with a custom position', () {
+    test('starts scanning from that position', () {
+      var scanner = new StringScanner('foo bar', position: 1);
+      expect(scanner.position, equals(1));
+      expect(scanner.rest, equals('oo bar'));
+
+      expect(scanner.scan(new RegExp('oo.')), isTrue);
+      expect(scanner.lastMatch[0], equals('oo '));
+      expect(scanner.position, equals(4));
+      expect(scanner.rest, equals('bar'));
+    });
+
+    test('throws an ArgumentError if the position is -1', () {
+      expect(() => new StringScanner('foo bar', position: -1),
+          throwsArgumentError);
+    });
+
+    test('throws an ArgumentError if the position is beyond the string', () {
+      expect(
+          () => new StringScanner('foo bar', position: 8), throwsArgumentError);
+    });
+  });
+}
diff --git a/mojo/public/dart/third_party/string_scanner/test/utils.dart b/mojo/public/dart/third_party/string_scanner/test/utils.dart
new file mode 100644
index 0000000..8df4b51
--- /dev/null
+++ b/mojo/public/dart/third_party/string_scanner/test/utils.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library string_scanner.test.utils;
+
+import 'package:string_scanner/string_scanner.dart';
+import 'package:test/test.dart';
+
+/// Returns a matcher that asserts that a closure throws a [FormatException]
+/// with the given [message].
+Matcher throwsStringScannerException(String text) {
+  return throwsA(predicate((error) {
+    expect(error, new isInstanceOf<StringScannerException>());
+    expect(error.span.text, equals(text));
+    return true;
+  }));
+}