WebRTC: Fix and enable -Woverloaded-virtual warnings.

webrtc/media/media.gyp

 # Copyright (c) 2016 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.
 
 {
   'includes': [ '../build/common.gypi', ],
@@ skipping 76 matching lines @@
         'sctp/sctpdataengine.h',
       ],
       # TODO(kjellander): Make the code compile without disabling these flags.
       # See https://bugs.chromium.org/p/webrtc/issues/detail?id=3307
       'cflags': [
         '-Wno-deprecated-declarations',
       ],
       'cflags!': [
         '-Wextra',
       ],
-      'cflags_cc!': [
-        '-Woverloaded-virtual',
-      ],
       'msvs_disabled_warnings': [
         4245,  # conversion from 'int' to 'size_t', signed/unsigned mismatch.
         4267,  # conversion from 'size_t' to 'int', possible loss of data.
         4389,  # signed/unsigned mismatch.
       ],
       'conditions': [
         ['build_libyuv==1', {
           'dependencies': ['<(DEPTH)/third_party/libyuv/libyuv.gyp:libyuv',],
         }],
         ['build_usrsctp==1', {
@@ skipping 36 matching lines @@
             'devices/gtkvideorenderer.h',
           ],
           'cflags': [
             '<!@(pkg-config --cflags gobject-2.0 gthread-2.0 gtk+-2.0)',
           ],
         }],
       ],
     },  # target rtc_media
   ],  # targets.
 }