Add support for cancellation of demuxer reads.

media/base/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.
 
 #ifndef MEDIA_BASE_DEMUXER_H_
 #define MEDIA_BASE_DEMUXER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 70 matching lines @@
 
   // Completes initialization of the demuxer.
   //
   // The demuxer does not own |host| as it is guaranteed to outlive the
   // lifetime of the demuxer. Don't delete it!  |status_cb| must only be run
   // after this method has returned.
   virtual void Initialize(DemuxerHost* host,
                           const PipelineStatusCB& status_cb,
                           bool enable_text_tracks) = 0;
 
+  // Aborts any pending read operations that the demuxer is involved with; any
+  // read aborted will be aborted with a status of kOk and an EOS buffer to

[wolenetz, 2016/08/24 23:46:55]

Why not re-use kAborted? ISTM even with this patch set, MSE will still return
kAborted (not kOk:EOS) if the stream is still enabled, just aborted.

[DaleCurtis, 2016/08/24 23:49:41]

Good point, I think this can just be kAborted without issue. I'll play around
with it, neither MSE nor SRC showed any problems.

[wolenetz, 2016/08/24 23:54:18]

SGTM. I'll look again at this in the morning. So far, nothing in MSE portion
otherwise strikes me as problematic.

+  // ensure that the process is non fatal to receiving clients.
+  virtual void AbortPendingReads() = 0;
+
   // Indicates that a new Seek() call is on its way. Implementations may abort
   // pending reads and future Read() calls may return kAborted until Seek() is
   // executed. |seek_time| is the presentation timestamp of the new Seek() call.
   //
   // In actual use, this call occurs on the main thread while Seek() is called
   // on the media thread. StartWaitingForSeek() can be used to synchronize the
   // two.
   //
   // StartWaitingForSeek() MUST be called before Seek().
   virtual void StartWaitingForSeek(base::TimeDelta seek_time) = 0;
@@ skipping 44 matching lines @@
       const std::vector<MediaTrack::Id>& track_ids,
       base::TimeDelta currTime) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Demuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DEMUXER_H_