fix build when ffmpeg, libvpx and libwebm are disabled

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 694 matching lines @@
           ],
         }],
         ['media_use_libwebm==1', {
           'dependencies': [
             '<(DEPTH)/third_party/libwebm/libwebm.gyp:libwebm',
           ],
           'sources': [
             'capture/webm_muxer.cc',
             'capture/webm_muxer.h',
           ],
+        }, {  # media_use_libwebm==0
+          'defines': [
+            'MEDIA_DISABLE_LIBWEBM',
+          ],
+          'direct_dependent_settings': {
+            'defines': [
+              'MEDIA_DISABLE_LIBWEBM',
+            ],
+          },
         }],
         ['enable_browser_cdms==1', {
           'sources': [
             'base/browser_cdm.cc',
             'base/browser_cdm.h',
             'base/browser_cdm_factory.cc',
             'base/browser_cdm_factory.h',
           ],
         }],
         ['OS=="android"', {
@@ skipping 1390 matching lines @@
               'dependencies': [
                 '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         },
       ],
     }],
   ],
 }