Android: Enable C99 mode instead of C89 (default).

webrtc/build/common.gypi

 # Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 # This file contains common settings for building WebRTC components.
 
@@ skipping 355 matching lines @@
         # Re-enable some warnings that Chromium disables.
         'msvs_disabled_warnings!': [4189,],
       }],
       ['OS=="android"', {
         'defines': [
           'WEBRTC_LINUX',
           'WEBRTC_ANDROID',
          ],
          'conditions': [
            ['clang==0', {
-             # The Android NDK doesn't provide optimized versions of these
-             # functions. Ensure they are disabled for all compilers.
              'cflags': [
+               # The Android NDK doesn't provide optimized versions of these
+               # functions. Ensure they are disabled for all compilers.
                '-fno-builtin-cos',
                '-fno-builtin-sin',
                '-fno-builtin-cosf',
                '-fno-builtin-sinf',
              ],
+             'cflags_c': [
+               # Use C99 mode instead of C89 (default).
+               '-std=c99',
+             ]
            }],
          ],
       }],
       ['include_internal_audio_device==1', {
         'defines': [
           'WEBRTC_INCLUDE_INTERNAL_AUDIO_DEVICE',
         ],
       }],
     ], # conditions
     'direct_dependent_settings': {
@@ skipping 52 matching lines @@
           # of a more specific macro.
           'defines': [
             'WEBRTC_POSIX',
           ],
         }],
       ],
     },
   }, # target_defaults
 }