MediaSource: Fix CHECK crash in append fudge room edge case.

media/filters/source_buffer_stream.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.
 
 // SourceBufferStream is a data structure that stores media Buffers in ranges.
 // Buffers can be appended out of presentation order. Buffers are retrieved by
 // seeking to the desired start point and calling GetNextBuffer(). Buffers are
 // returned in sequential presentation order.
 
 #ifndef MEDIA_FILTERS_SOURCE_BUFFER_STREAM_H_
@@ skipping 61 matching lines @@
   // starting at |coded_frame_group_start_time|.
   // TODO(acolwell/wolenetz): This should be changed to a presentation
   // timestamp. See http://crbug.com/402502
   void OnStartOfCodedFrameGroup(DecodeTimestamp coded_frame_group_start_time);
 
   // Add the |buffers| to the SourceBufferStream. Buffers within the queue are
   // expected to be in order, but multiple calls to Append() may add buffers out
   // of order or overlapping. Assumes all buffers within |buffers| are in
   // presentation order and are non-overlapping.
   // Returns true if Append() was successful, false if |buffers| are not added.
-  // TODO(vrk): Implement garbage collection. (crbug.com/125070)

[wolenetz, 2016/10/05 22:41:09]

:)

   bool Append(const BufferQueue& buffers);
 
   // Removes buffers between |start| and |end| according to the steps
   // in the "Coded Frame Removal Algorithm" in the Media Source
   // Extensions Spec.
   // https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html#sourcebuffer-coded-frame-removal
   //
   // |duration| is the current duration of the presentation. It is
   // required by the computation outlined in the spec.
   void Remove(base::TimeDelta start, base::TimeDelta end,
@@ skipping 140 matching lines @@
   void SetSelectedRange(SourceBufferRange* range);
 
   // Seeks |range| to |seek_timestamp| and then calls SetSelectedRange() with
   // |range|.
   void SeekAndSetSelectedRange(SourceBufferRange* range,
                                DecodeTimestamp seek_timestamp);
 
   // Resets this stream back to an unseeked state.
   void ResetSeekState();
 
+  // Reset state tracking various metadata about the last appended buffer.
+  void ResetLastAppendedState();
+
   // Returns true if |seek_timestamp| refers to the beginning of the first range
   // in |ranges_|, false otherwise or if |ranges_| is empty.
   bool ShouldSeekToStartOfBuffered(base::TimeDelta seek_timestamp) const;
 
   // Returns true if the timestamps of |buffers| are monotonically increasing
   // since the previous append to the coded frame group, false otherwise.
   bool IsMonotonicallyIncreasing(const BufferQueue& buffers);
 
   // Returns true if |selected_range_| is the only range in |ranges_| that
   // HasNextBufferPosition().
@@ skipping 61 matching lines @@
   // match |start| are not removed. If set to false, buffers with
   // timestamps that match |start| will be removed.
   // |*deleted_buffers| - Filled with buffers for the current playback position
   // if the removal range included the current playback position. These buffers
   // can be used as candidates for placing in the |track_buffer_|.
   void RemoveInternal(DecodeTimestamp start,
                       DecodeTimestamp end,
                       bool exclude_start,
                       BufferQueue* deleted_buffers);
 
+  // Helper function used by RemoveInternal() to evaluate whether remove will
+  // disrupt the last appended GOP. If disruption is expected, reset state
+  // tracking the last append. This will trigger frame filtering in Append()
+  // until a new key frame is provided.
+  void UpdateLastAppendStateForRemove(DecodeTimestamp remove_start,
+                                      DecodeTimestamp remove_end,
+                                      bool exclude_start);
+
   Type GetType() const;
 
   // See GetNextBuffer() for additional details.  This method handles splice
   // frame processing.
   Status HandleNextBufferWithSplice(
       scoped_refptr<StreamParserBuffer>* out_buffer);
 
   // See GetNextBuffer() for additional details.  This method handles preroll
   // frame processing.
   Status HandleNextBufferWithPreroll(
@@ skipping 126 matching lines @@
   int num_track_buffer_gap_warning_logs_ = 0;
   int num_garbage_collect_algorithm_logs_ = 0;
   int num_strange_same_timestamps_logs_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SourceBufferStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_SOURCE_BUFFER_STREAM_H_