Refactor BlockDifference() to use MediaInitializer().

media/media.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
     # Override to dynamically link the cras (ChromeOS audio) library.
     'use_cras%': 0,
     # Option e.g. for Linux distributions to link pulseaudio directly
@@ skipping 851 matching lines @@
             'mp4/offset_byte_queue.cc',
             'mp4/offset_byte_queue.h',
             'mp4/track_run_iterator.cc',
             'mp4/track_run_iterator.h',
           ],
         }],
         ['screen_capture_supported==1', {
           'dependencies': [
             '../third_party/webrtc/modules/modules.gyp:desktop_capture',
           ],
+          'defines': [
+            'SCREEN_CAPTURE_SUPPORTED',
+          ],
         }, {
           'sources/': [
             ['exclude', '^video/capture/screen/'],
           ],
         }],
         ['toolkit_uses_gtk==1', {
           'dependencies': [
             '../build/linux/system.gyp:gtk',
           ],
         }],
@@ skipping 821 matching lines @@
           'sources': [
             'tools/media_bench/media_bench.cc',
           ],
           # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
           'msvs_disabled_warnings': [ 4267, ],
         },
       ],
     }],
   ],
 }