Enable webkit.gyp compiler warnings on mac only.

webkit/webkit.gyp

 # Copyright (c) 2009 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.
 
 {
   'includes': [
     '../third_party/WebKit/WebCore/WebCore.gypi',
   ],
   'variables': {
     # TODO: remove this helper when we have loops in GYP
     'apply_locales_cmd': ['python', '../chrome/tools/build/apply_locales.py',],
+
+    # We can't turn on warnings on Windows and Linux until we upstream the
+    # WebKit API.
+    'conditions': [
+      ['OS=="mac"', {
+        'chromium_code': 1,
+      }],
+    ],
   },
   'targets': [
     {
       # Currently, builders assume webkit.sln builds test_shell on windows.
       # We should change this, but for now allows trybot runs.
       # for now.
       'target_name': 'pull_in_test_shell',
       'type': 'none',
       'conditions': [
         ['OS=="win"', {
@@ skipping 628 matching lines @@
           'files': [
 
             '<@(webinspector_image_files)',
 
           ],
         },
       ],
     },
   ], # targets
 }