Remove buffer duration calculation from WebMClusterParser and update SourceBufferStream accordingly

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 fa1b9442cfcc849bfe20e586b4d557267405aa38..7352aa4a7fc475773404bd511ad6e38b8873b05d 100644
--- a/media/base/stream_parser_buffer.h
+++ b/media/base/stream_parser_buffer.h
@@ -17,9 +17,6 @@ class MEDIA_EXPORT StreamParserBuffer : public DecoderBuffer {
       const uint8* data, int data_size, bool is_keyframe);
   bool IsKeyframe() const { return is_keyframe_; }
 
-  // Returns this buffer's timestamp + duration, assuming both are valid.
-  base::TimeDelta GetEndTimestamp() const;
-
  private:
   StreamParserBuffer(const uint8* data, int data_size, bool is_keyframe);
   virtual ~StreamParserBuffer();