Unsigned warning fix - take 2

build/common.gypi

 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   'variables': {
     # .gyp files or targets should set chromium_code to 1 if they build
@@ skipping 536 matching lines @@
           }],
           ['OS!="linux"', {
             'sources/': [
               ['exclude', '_linux(_unittest)?\\.cc$'],
               ['exclude', '/linux/'],
             ],
           }],
           # We use "POSIX" to refer to all non-Windows operating systems.
           ['OS=="win"', {
             'sources/': [ ['exclude', '_posix\\.cc$'] ],
+            # turn on warnings for signed/unsigned mismatch on chromium code.
+            'msvs_settings': {
+              'VCCLCompilerTool': {
+                'AdditionalOptions': ['/we4389'],
+              },
+            },
           }],
           # Though Skia is conceptually shared by Linux and Windows,
           # the only _skia files in our tree are Linux-specific.
           ['OS!="linux" and OS!="freebsd" and OS!="openbsd"', {
             'sources/': [ ['exclude', '_skia\\.cc$'] ],
           }],
           ['chromeos!=1', {
             'sources/': [ ['exclude', '_chromeos\\.cc$'] ]
           }],
           ['toolkit_views==0', {
@@ skipping 797 matching lines @@
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }
 
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 # indent-tabs-mode:nil
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