[Media, Video] Enable the video track for a new renderer.

media/filters/pipeline_controller.cc

 // Copyright 2016 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.
 
 #include "media/filters/pipeline_controller.h"
 
 #include "base/bind.h"
 #include "media/base/demuxer.h"
 
 namespace media {
 
 PipelineController::PipelineController(
     Pipeline* pipeline,
     const RendererFactoryCB& renderer_factory_cb,
     const SeekedCB& seeked_cb,
     const SuspendedCB& suspended_cb,
+    const ResumedCB& resumed_cb,
     const PipelineStatusCB& error_cb)
     : pipeline_(pipeline),
       renderer_factory_cb_(renderer_factory_cb),
       seeked_cb_(seeked_cb),
       suspended_cb_(suspended_cb),
+      resumed_cb_(resumed_cb),
       error_cb_(error_cb),
       weak_factory_(this) {
   DCHECK(pipeline_);
   DCHECK(!renderer_factory_cb_.is_null());
   DCHECK(!seeked_cb_.is_null());
   DCHECK(!suspended_cb_.is_null());
+  DCHECK(!resumed_cb_.is_null());
   DCHECK(!error_cb_.is_null());
 }
 
 PipelineController::~PipelineController() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 // TODO(sandersd): If there is a pending suspend, don't call pipeline_.Start()
 // until Resume().
 void PipelineController::Start(Demuxer* demuxer,
@@ skipping 135 matching lines @@
       pending_time_updated_ = true;
     }
 
     // Tell |demuxer_| to expect our resume.
     DCHECK(!waiting_for_seek_);
     waiting_for_seek_ = true;
     demuxer_->StartWaitingForSeek(seek_time_);
 
     pending_resume_ = false;
     state_ = State::RESUMING;
+    pending_resumed_cb_ = true;
     pipeline_->Resume(renderer_factory_cb_.Run(), seek_time_,
                       base::Bind(&PipelineController::OnPipelineStatus,
                                  weak_factory_.GetWeakPtr(), State::PLAYING));
     return;
   }
 
   // If we have pending operations, and a seek is ongoing, abort it.
   if ((pending_seek_ || pending_suspend_) && waiting_for_seek_) {
     // If there is no pending seek, return the current seek to pending status.
     if (!pending_seek_) {
@@ skipping 30 matching lines @@
   if (state_ == State::PLAYING) {
     if (pending_seeked_cb_) {
       // |seeked_cb_| may be reentrant, so update state first and return
       // immediately.
       pending_seeked_cb_ = false;
       bool was_pending_time_updated = pending_time_updated_;
       pending_time_updated_ = false;
       seeked_cb_.Run(was_pending_time_updated);
       return;
     }
+
+    if (pending_resumed_cb_) {
+      pending_resumed_cb_ = false;
+      resumed_cb_.Run();

[sandersd (OOO until July 31), 2017/01/07 00:56:17]

This won't be called if |pending_seeked_cb_| is true.

The cleanest alternative I can think of is to make it an immediate callback
instead of a stable state callback. I'm not sure which semantics are better for
you, but moving this to OnPipelineStatus() means we won't have to worry about
the reentrancy of |seeked_cb_|.

It's probably okay to just move it above the seek callback as well. We can
require that the resume CB is non-reentrant as a matter of API documentation.

[whywhat, 2017/01/07 02:02:35]

Done. Would checking for state_ to be RESUMING and state be PLAYING in
OnPipelineStatus be a good enough condition so I could eliminate the
pending_resumed_cb_ var?
As long as the RendererImpl calls InitializeVideoRenderer by this moment (and I
think it does), that should be enough for the bug I'm fixing.

+    }
   }
 }
 
 }  // namespace media