[AUTO UPDATE] Copying from upstream Mojo Repository.
caa382ebd4d5175136dc148a774e3f0d52294954
  Tue, 21 Jun 2016 12:31:22 -0700, jamesr@chromium.org
  Enable Wextra and Wno-unused-parameters in default cflags

config/compiler/BUILD.gn

diff --git a/config/compiler/BUILD.gn b/config/compiler/BUILD.gn
index d570de1..24103ad 100644
--- a/config/compiler/BUILD.gn
+++ b/config/compiler/BUILD.gn
@@ -829,6 +829,8 @@
     # code generated by flex (used in angle) contains that keyword.
     # http://crbug.com/255186
     "-Wno-deprecated-register",
+
+    "-Wno-unused-parameter",
   ]
 
   # NaCl's Clang compiler and Chrome's hermetic Clang compiler will almost
@@ -851,12 +853,7 @@
 config("chromium_code") {
   cflags = [
     "-Wall",
-
-    # GCC turns on -Wsign-compare for C++ under -Wall, but clang doesn't,
-    # so we specify it explicitly.
-    # TODO(fischman): remove this if http://llvm.org/PR10448 obsoletes it.
-    # http://code.google.com/p/chromium/issues/detail?id=90453
-    "-Wsign-compare",
+    "-Wextra",
   ]
 
   # In Chromium code, we define __STDC_foo_MACROS in order to get the