[WIP] Supporting arm_neon_optional flag for blink platform.

Source/wtf/wtf.gyp

 # Copyright (C) 2012 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 134 matching lines @@
             ]
           }
         }, { # OS!="mac"
           'sources/': [
             ['exclude', 'CF\\.cpp$'],
             ['exclude', 'Mac\\.mm$'],
             # mac is the only OS that uses WebKit's copy of TCMalloc.
             ['exclude', 'TC.*\\.(cpp|h)$'],
           ],
         }],
+        ['target_arch=="arm" and OS == "android"', {
+          'includes': [
+            '../../../../build/android/cpufeatures.gypi',
+          ],
+        }],
       ],
     },
   ]
 }