Replace MockFilterCallback with MockCallback and simplify unit tests.

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,
     'player_x11_renderer%': 'x11',
   },
   'targets': [
@@ skipping 260 matching lines @@
         'audio/fake_audio_input_stream_unittest.cc',
         'audio/linux/alsa_output_unittest.cc',
         'audio/mac/audio_output_mac_unittest.cc',
         'audio/simple_sources_unittest.cc',
         'audio/win/audio_output_win_unittest.cc',
         'base/composite_filter_unittest.cc',
         'base/clock_impl_unittest.cc',
         'base/data_buffer_unittest.cc',
         'base/djb2_unittest.cc',
         'base/filter_collection_unittest.cc',
+        'base/mock_callback.cc',
+        'base/mock_callback.h',
         'base/mock_ffmpeg.cc',
         'base/mock_ffmpeg.h',
         'base/mock_reader.h',
         'base/mock_task.cc',
         'base/mock_task.h',
         'base/pipeline_impl_unittest.cc',
         'base/pts_heap_unittest.cc',
         'base/run_all_unittests.cc',
         'base/seekable_buffer_unittest.cc',
         'base/state_matrix_unittest.cc',
@@ skipping 352 matching lines @@
       ],
     }],
   ],
 }
 
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