Add video decoding methods in Decryptor and add DecryptingVideoDecoder.

media/filters/ffmpeg_video_decoder.cc

 // 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.
 
 #include "media/filters/ffmpeg_video_decoder.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 161 matching lines @@
       &FFmpegVideoDecoder::DoRead, this, read_cb));
 }
 
 void FFmpegVideoDecoder::Reset(const base::Closure& closure) {
   if (!message_loop_->BelongsToCurrentThread()) {
     message_loop_->PostTask(FROM_HERE, base::Bind(
         &FFmpegVideoDecoder::Reset, this, closure));
     return;
   }
 
+  DCHECK(reset_cb_.is_null());
   reset_cb_ = closure;
 
   // Defer the reset if a read is pending.
   if (!read_cb_.is_null())
     return;
 
   DoReset();
 }
 
 void FFmpegVideoDecoder::DoReset() {
   DCHECK(read_cb_.is_null());
 
   avcodec_flush_buffers(codec_context_);
   state_ = kNormal;
   reset_cb_.Run();
   reset_cb_.Reset();
 }
 
 void FFmpegVideoDecoder::Stop(const base::Closure& closure) {
   if (!message_loop_->BelongsToCurrentThread()) {
     message_loop_->PostTask(FROM_HERE, base::Bind(
         &FFmpegVideoDecoder::Stop, this, closure));
     return;
   }
 
+  DCHECK(stop_cb_.is_null());
+  stop_cb_ = closure;
+
   if (decryptor_)
     decryptor_->Stop();
 
-  stop_cb_ = closure;
-
   // Defer stopping if a read is pending.
   if (!read_cb_.is_null())
     return;
 
   DoStop();
 }
 
 void FFmpegVideoDecoder::DoStop() {
   ReleaseFFmpegResources();
   state_ = kUninitialized;
@@ skipping 301 matching lines @@
     return false;
 
   if (avcodec_open2(codec_context_, codec, NULL) < 0)
     return false;
 
   av_frame_ = avcodec_alloc_frame();
   return true;
 }
 
 }  // namespace media