Rewrite media::Pipeline state transition machinery and simplify shutdown.

media/base/pipeline_status.h

 // 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.
 
 #ifndef MEDIA_BASE_PIPELINE_STATUS_H_
 #define MEDIA_BASE_PIPELINE_STATUS_H_
 
 #include "base/callback.h"
 
 #include <string>
 
 namespace media {
 
 // Status states for pipeline.  All codes except PIPELINE_OK indicate errors.
 // Logged to UMA, so never reuse a value, always add new/greater ones!
 // TODO(vrk/scherkus): Trim the unused status codes. (crbug.com/126070)
 enum PipelineStatus {
   PIPELINE_OK = 0,
   PIPELINE_ERROR_URL_NOT_FOUND = 1,
   PIPELINE_ERROR_NETWORK = 2,
   PIPELINE_ERROR_DECODE = 3,
   PIPELINE_ERROR_DECRYPT = 4,
   PIPELINE_ERROR_ABORT = 5,
   PIPELINE_ERROR_INITIALIZATION_FAILED = 6,
-  PIPELINE_ERROR_REQUIRED_FILTER_MISSING = 7,
   PIPELINE_ERROR_COULD_NOT_RENDER = 8,
   PIPELINE_ERROR_READ = 9,
   PIPELINE_ERROR_OPERATION_PENDING = 10,
   PIPELINE_ERROR_INVALID_STATE = 11,
   // Demuxer related errors.
   DEMUXER_ERROR_COULD_NOT_OPEN = 12,
   DEMUXER_ERROR_COULD_NOT_PARSE = 13,
   DEMUXER_ERROR_NO_SUPPORTED_STREAMS = 14,
   // Decoder related errors.
   DECODER_ERROR_NOT_SUPPORTED = 15,
@@ skipping 21 matching lines @@
   uint32 video_frames_decoded;
   uint32 video_frames_dropped;
 };
 
 // Used for updating pipeline statistics.
 typedef base::Callback<void(const PipelineStatistics&)> StatisticsCB;
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_PIPELINE_STATUS_H_