Add extra warnings to match what Android uses.

platform_tools/android/gyp/dependencies.gypi

 # This GYP file stores the dependencies necessary to build Skia on the Android
 # platform. The OS doesn't provide many stable libraries as part of the
 # distribution so we have to build a few of them ourselves.
 #
 # NOTE: We tried adding the gyp file to the android/ directory at the root of
 # the Skia repo, but that resulted in the generated makefiles being created
 # outside of the out directory. We may be able to move the bulk of this gyp
 # to the /android directory and put a simple shim here, but that has yet to be
 # tested.
 
@@ skipping 53 matching lines @@
       ],
       'include_dirs': [
         '../third_party/externals/gif',
       ],
       'cflags': [
         '-Wno-format',
         '-DHAVE_CONFIG_H',
       ],
       'cflags!': [
         '-Wall',
+        '-Wextra',

[mtklein, 2013/11/18 21:21:56]

Maybe just cflags: [ '-w' ] these guys?

[djsollen, 2013/11/18 21:34:04]

Done.

       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../third_party/externals/gif',
         ],
       }
     },
     {
       'target_name': 'png',
       'type': 'static_library',
@@ skipping 17 matching lines @@
         '../third_party/externals/png/pngwutil.c',
       ],
       'include_dirs': [
         '../third_party/externals/png',
       ],
       'cflags': [
         '-fvisibility=hidden',
       ],
       'cflags!': [
         '-Wall',
+        '-Wextra',
       ],
       'link_settings': {
         'libraries': [
           '-lz',
         ],
       },
       'direct_dependent_settings': {
         'include_dirs': [
           '../third_party/externals/png',
         ],
@@ skipping 119 matching lines @@
           }],
         ],
         'sources': [
           '../app/jni/com_skia_SkiaSampleRenderer.cpp',
         ],
       },
 
     },
   ]
 }