Add support for cancellation of demuxer reads.

media/base/pipeline_impl.cc

Index: media/base/pipeline_impl.cc
diff --git a/media/base/pipeline_impl.cc b/media/base/pipeline_impl.cc
index 43fdf5eb951113bab49777c1f94e89b3dc55434e..08817780663251f95d48e6abc0afc65e12c65b0a 100644
--- a/media/base/pipeline_impl.cc
+++ b/media/base/pipeline_impl.cc
@@ -311,6 +311,9 @@ void PipelineImpl::RendererWrapper::Seek(base::TimeDelta time) {
   DCHECK(!pending_callbacks_);
   SerialRunner::Queue bound_fns;
 
+  // Abort any reads the renderer may be blocked on.
+  demuxer_->AbortPendingReads();

[wolenetz, 2016/08/25 18:56:14]

Would this be better integrated with how the MSE path needs the abort already
via PipelineController::Dispatch()'s calls to StartWaitingForSeek() and
CancelPendingSeek() (with appropriate implementation in FFmpegDemuxer of these
two methods to do the necessary abort tracking)?

This would let rapid sequential FFmpeg seeks cancel a previous incomplete seek
to satisfy a more recent one, just like in MSE case.

Perhaps this optimization could be done in a follow-up CL.

[DaleCurtis, 2016/08/29 21:14:58]

Good point. I think we just need to add AbortPendingReads() to
CancelPendingSeek() -- which is what I've done.

[wolenetz, 2016/08/30 18:52:12]

Acknowledged.

+
   // Pause.
   if (text_renderer_) {
     bound_fns.Push(base::Bind(&TextRenderer::Pause,
@@ -352,8 +355,7 @@ void PipelineImpl::RendererWrapper::Suspend() {
 
   SetState(kSuspending);
 
-  // Freeze playback and record the media time before flushing. (Flushing clears
-  // the value.)
+  // Freeze playback and record the media time before destroying the renderer.
   shared_state_.renderer->SetPlaybackRate(0.0);
   {
     base::AutoLock auto_lock(shared_state_lock_);
@@ -361,6 +363,9 @@ void PipelineImpl::RendererWrapper::Suspend() {
     DCHECK(shared_state_.suspend_timestamp != kNoTimestamp);
   }
 
+  // Abort any reads the renderer may be blocked on.
+  demuxer_->AbortPendingReads();
+
   // Queue the asynchronous actions required to stop playback.
   SerialRunner::Queue fns;
 
@@ -369,14 +374,7 @@ void PipelineImpl::RendererWrapper::Suspend() {
                         base::Unretained(text_renderer_.get())));
   }
 
-  fns.Push(base::Bind(&Renderer::Flush,
-                      base::Unretained(shared_state_.renderer.get())));
-
-  if (text_renderer_) {
-    fns.Push(base::Bind(&TextRenderer::Flush,
-                        base::Unretained(text_renderer_.get())));
-  }
-
+  // No need to flush the renderer since it's going to be destroyed.
   pending_callbacks_ = SerialRunner::Run(
       fns, base::Bind(&RendererWrapper::CompleteSuspend, weak_this_));
 }