Fix MP4StreamParser discard behavior when retaining 'moof'.

media/mp4/mp4_stream_parser.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_MP4_MP4_STREAM_PARSER_H_
 #define MEDIA_MP4_MP4_STREAM_PARSER_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 32 matching lines @@
     kEmittingSamples,
     kError
   };
 
   bool ParseBox(bool* err);
   bool ParseMoov(mp4::BoxReader* reader);
   bool ParseMoof(mp4::BoxReader* reader);
 
   bool EmitKeyNeeded(const TrackEncryption& track_encryption);
 
-  bool ReadMDATsUntil(const int64 tgt_tail);
+  // To retain proper framing, each 'mdat' atom must be read; to limit memory
+  // usage, the atom's data needs to be discarded incrementally as frames are
+  // extracted from the stream. This function discards data from the stream up
+  // to |tgt_offset|, updating the |mdat_tail_| value so that framing can be
+  // retained after all 'mdat' information has been read.
+  // Returns 'true' on success, 'false' if there was an error.
+  bool ReadAndDiscardMDATsUntil(const int64 tgt_tail);

[acolwell GONE FROM CHROMIUM, 2012/08/01 16:39:02]

nits: How about just using offset for the parameter name or spell out target
instead of tgt? Update comment to match the parameter name. 

[strobe_, 2012/08/01 19:01:33]

Done.

 
   void ChangeState(State new_state);
 
   bool EmitConfigs();
   bool PrepareAVCBuffer(const AVCDecoderConfigurationRecord& avc_config,
                         std::vector<uint8>* frame_buf,
                         std::vector<SubsampleEntry>* subsamples) const;
   bool EnqueueSample(BufferQueue* audio_buffers,
                      BufferQueue* video_buffers,
                      bool* err);
@@ skipping 30 matching lines @@
   uint32 video_track_id_;
   bool has_sbr_;
 
   DISALLOW_COPY_AND_ASSIGN(MP4StreamParser);
 };
 
 }  // namespace mp4
 }  // namespace media
 
 #endif  // MEDIA_MP4_MP4_STREAM_PARSER_H_