win: pull gyp for gn generation

and #if out some code that causes "unreachable code" warning on windows.

TBR=jam@chromium.org
BUG=

Review URL: https://codereview.chromium.org/694253003
diff --git a/DEPS b/DEPS
index 68073d8..3b3fb1a 100644
--- a/DEPS
+++ b/DEPS
@@ -156,11 +156,13 @@
   },
   'win': {
     'src/third_party/nss':
-     Var('chromium_git') + '/chromium/deps/nss.git' + '@' + Var('nss_revision'),
+        Var('chromium_git') + '/chromium/deps/nss.git' + '@' + Var('nss_revision'),
     'src/third_party/bison':
-     Var('chromium_git') + '/chromium/deps/bison.git' + '@' + '083c9a45e4affdd5464ee2b224c2df649c6e26c3',
+        Var('chromium_git') + '/chromium/deps/bison.git' + '@' + '083c9a45e4affdd5464ee2b224c2df649c6e26c3',
     'src/third_party/gperf':
-     Var('chromium_git') + '/chromium/deps/gperf.git' + '@' + 'd892d79f64f9449770443fb06da49b5a1e5d33c1',
+        Var('chromium_git') + '/chromium/deps/gperf.git' + '@' + 'd892d79f64f9449770443fb06da49b5a1e5d33c1',
+    'src/tools/gyp':
+        Var('chromium_git') + '/external/gyp.git' + '@' + '487c0b6ae8b44932e45347211bca0e8387718436', # from svn revision 1998
   }
 }
 
diff --git a/mojo/common/data_pipe_utils.cc b/mojo/common/data_pipe_utils.cc
index d3ada62..0598fba 100644
--- a/mojo/common/data_pipe_utils.cc
+++ b/mojo/common/data_pipe_utils.cc
@@ -100,8 +100,10 @@
       return result == MOJO_RESULT_FAILED_PRECONDITION;
     }
   }
+#if !defined(OS_WIN)
   NOTREACHED();
   return false;
+#endif
 }
 
 } // namespace