Disable CLANG_WARN_CXX0X_EXTENSIONS (-Wc++0x-extensions) when building with clang under Xcode 4

build/common.gypi

 # Copyright (c) 2011 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 expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 2074 matching lines @@
             # pattern.
             '-Wno-missing-field-initializers',
           ],
           'conditions': [
             ['chromium_mac_pch', {'GCC_PRECOMPILE_PREFIX_HEADER': 'YES'},
                                  {'GCC_PRECOMPILE_PREFIX_HEADER': 'NO'}
             ],
             ['clang==1', {
               'CC': '$(SOURCE_ROOT)/<(clang_dir)/clang',
               'LDPLUSPLUS': '$(SOURCE_ROOT)/<(clang_dir)/clang++',
+
+              # Don't use -Wc++0x-extensions, which Xcode 4 enables by default
+              # when buliding with clang. This warning is triggered when the
+              # override keyword is used via the OVERRIDE macro from
+              # base/compiler_specific.h.
+              'CLANG_WARN_CXX0X_EXTENSIONS': 'NO',
+
               'GCC_VERSION': 'com.apple.compilers.llvm.clang.1_0',
               'WARNING_CFLAGS': [
                 '-Wheader-hygiene',
+
                 # Don't die on dtoa code that uses a char as an array index.
                 # This is required solely for base/third_party/dmg_fp/dtoa.cc.
                 '-Wno-char-subscripts',
+
                 # Clang spots more unused functions.
                 '-Wno-unused-function',
+
                 # See comments on this flag higher up in this file.
                 '-Wno-unnamed-type-template-args',
+
                 # TODO(thakis): Reenable once the one instance this warns on
                 # is fixed.
                 '-Wno-parentheses',
               ],
             }],
             ['clang==1 and clang_use_chrome_plugins==1', {
               'OTHER_CFLAGS': [
                 '<(clang_chrome_plugins_flags)',
               ],
             }],
@@ skipping 352 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }