Fix race on demuxer memory usage. Reuse previous calculation.

media/filters/ffmpeg_demuxer.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.
 
 // Implements the Demuxer interface using FFmpeg's libavformat.  At this time
 // will support demuxing any audio/video format thrown at it.  The streams
 // output mime types audio/x-ffmpeg and video/x-ffmpeg and include an integer
 // key FFmpegCodecID which contains the CodecID enumeration value.  The CodecIDs
 // can be used to create and initialize the corresponding FFmpeg decoder.
 //
@@ skipping 215 matching lines @@
   void OnSeekFrameDone(const PipelineStatusCB& cb, int result);
 
   // FFmpeg callbacks during reading + helper method to initiate reads.
   void ReadFrameIfNeeded();
   void OnReadFrameDone(ScopedAVPacket packet, int result);
 
   // Returns true iff any stream has additional capacity. Note that streams can
   // go over capacity depending on how the file is muxed.
   bool StreamsHaveAvailableCapacity();
 
-  // Returns true if the maximum allowed memory usage has been reached.
-  bool IsMaxMemoryUsageReached() const;
+  // Updates |stream_memory_usage_| to the memory usage in bytes of all
+  // FFmpegDemuxerStreams.  Returns the current memory usage.
+  int64_t UpdateMemoryUsage();
 
   // Signal all FFmpegDemuxerStreams that the stream has ended.
   void StreamHasEnded();
 
   // Called by |url_protocol_| whenever |data_source_| returns a read error.
   void OnDataSourceError();
 
   // Returns the stream from |streams_| that matches |type| as an
   // FFmpegDemuxerStream.
   FFmpegDemuxerStream* GetFFmpegStream(DemuxerStream::Type type) const;
@@ skipping 68 matching lines @@
   // Set if we know duration of the audio stream. Used when processing end of
   // stream -- at this moment we definitely know duration.
   bool duration_known_;
 
   // FFmpegURLProtocol implementation and corresponding glue bits.
   scoped_ptr<BlockingUrlProtocol> url_protocol_;
   scoped_ptr<FFmpegGlue> glue_;
 
   const EncryptedMediaInitDataCB encrypted_media_init_data_cb_;
 
+  // Last stream size as calculated by UpdateMemoryUsage().
+  mutable base::Lock stream_memory_usage_lock_;
+  int64_t stream_memory_usage_;
+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<FFmpegDemuxer> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegDemuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_DEMUXER_H_