Remove media::VideoDecodeContext as it has no implementation and is unused.

media/media.gyp

 # Copyright (c) 2011 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 PulseAudio library.
     'use_pulseaudio%': 0,
   },
@@ skipping 633 matching lines @@
       ],
       'sources': [
         'audio/test_audio_input_controller_factory.cc',
         'audio/test_audio_input_controller_factory.h',
         'base/mock_callback.cc',
         'base/mock_callback.h',
         'base/mock_filter_host.cc',
         'base/mock_filter_host.h',
         'base/mock_filters.cc',
         'base/mock_filters.h',
-        'video/video_mock_objects.cc',
-        'video/video_mock_objects.h',
       ],
     },
     {
       'target_name': 'scaler_bench',
       'type': 'executable',
       'dependencies': [
         'media',
         'yuv_convert',
         '../base/base.gyp:base',
         '../skia/skia.gyp:skia',
@@ skipping 217 matching lines @@
             '../third_party/ffmpeg/ffmpeg.gyp:ffmpeg',
           ],
           'sources': [
             'tools/media_bench/media_bench.cc',
           ],
         },
       ],
     }]
   ],
 }