Fix the untrusted builds of Chrome on ARM.

build/common_untrusted.gypi

 # Copyright (c) 2012 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.
 
 # This GYP file should be included for every target in Chromium that is built
 # using the NaCl toolchain.
 {
   'includes': [
     '../native_client/build/untrusted.gypi',
   ],
   'target_defaults': {
     'variables': {
       'conditions': [
         ['target_arch=="arm"', {
           'clang': 1,
           'defines': [
             # Needed by build/build_config.h processor architecture detection.
             '__ARMEL__',
             # Needed by base/third_party/nspr/prtime.cc.
             '__arm__',
             # Disable ValGrind. The assembly code it generates causes the build
             # to fail.
             'NVALGRIND',
           ],
+          'compile_flags': [
+             # Disable C++ 11 extensions. Chrome's OVERRIDE macro will generate
+             # warnings that cause the build to fail.
+             '-Wno-c++11-extensions',
+          ],
         }],
       ],
     },
   },
 }