Add gapless playback support for AAC playback.

media/base/stream_parser_buffer.h

Index: media/base/stream_parser_buffer.h
diff --git a/media/base/stream_parser_buffer.h b/media/base/stream_parser_buffer.h
index 9c077c1235d7ce2132f6ba9734fb95d10ecc5407..21af4f78f9db9de8bb25608700834cb48d83370b 100644
--- a/media/base/stream_parser_buffer.h
+++ b/media/base/stream_parser_buffer.h
@@ -51,7 +51,8 @@ class MEDIA_EXPORT StreamParserBuffer : public DecoderBuffer {
   TrackId track_id() const { return track_id_; }
 
   // Converts this buffer to a splice buffer.  |pre_splice_buffers| must not
-  // have any  EOS buffers and must not have any nested splice buffers.
+  // have any EOS buffers, must not have any splice buffers, nor must have any
+  // buffer with preroll.
   //
   // |pre_splice_buffers| will be deep copied and each copy's splice_timestamp()
   // will be set to this buffer's splice_timestamp().  A copy of |this|, with a
@@ -63,6 +64,20 @@ class MEDIA_EXPORT StreamParserBuffer : public DecoderBuffer {
   void ConvertToSpliceBuffer(const BufferQueue& pre_splice_buffers);
   const BufferQueue& get_splice_buffers() const { return splice_buffers_; }
 
+  // Specifies a buffer which must be decoded prior to this one to ensure this
+  // buffer can be accurately decoded.  The given buffer must be of the same
+  // type, must not be a splice buffer, must not have any discard padding, and
+  // must not be an end of stream buffer.  |preroll| is not copied.
+  //
+  // It's expected that this preroll buffer will be discarded entirely post
+  // decoding.  As such it's discard_padding() will be set to its duration().
+  //
+  // All future timestamp, decode timestamp, config id, or track id changes to
+  // this buffer will be applied to the preroll buffer as well.  These values
+  // will be applied when GetPrerollBuffer() is called.
+  void SetPrerollBuffer(const scoped_refptr<StreamParserBuffer>& preroll);
+  const scoped_refptr<StreamParserBuffer>& GetPrerollBuffer();
+
  private:
   StreamParserBuffer(const uint8* data, int data_size,
                      const uint8* side_data, int side_data_size,
@@ -75,8 +90,8 @@ class MEDIA_EXPORT StreamParserBuffer : public DecoderBuffer {
   int config_id_;
   Type type_;
   TrackId track_id_;
-
   BufferQueue splice_buffers_;
+  scoped_refptr<StreamParserBuffer> preroll_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(StreamParserBuffer);
 };