Move destruction of VEAEncoder to encoding task runner

content/renderer/media_recorder/video_track_recorder.cc

Index: content/renderer/media_recorder/video_track_recorder.cc
diff --git a/content/renderer/media_recorder/video_track_recorder.cc b/content/renderer/media_recorder/video_track_recorder.cc
index d77d300d8da957f3b0675927fff963acca09c093..92b20bc92cd36ea17ae421bd61e0d3f08a615e31 100644
--- a/content/renderer/media_recorder/video_track_recorder.cc
+++ b/content/renderer/media_recorder/video_track_recorder.cc
@@ -449,6 +449,8 @@ class VEAEncoder final : public VideoTrackRecorder::Encoder,
                                   base::TimeTicks capture_timestamp) override;
   void ConfigureEncoderOnEncodingTaskRunner(const gfx::Size& size) override;
 
+  void DestroyOnEncodingTaskRunner(base::WaitableEvent* async_waiter);
+
   media::GpuVideoAcceleratorFactories* const gpu_factories_;
 
   const media::VideoCodecProfile codec_;
@@ -585,9 +587,17 @@ VEAEncoder::VEAEncoder(
 }
 
 VEAEncoder::~VEAEncoder() {
+  DVLOG(3) << __func__;

[mcasas, 2017/03/15 01:14:17]

nit: remove the DVLOG()s

[emircan, 2017/03/15 01:36:18]

Done.

+
+  base::WaitableEvent release_waiter(
+      base::WaitableEvent::ResetPolicy::MANUAL,
+      base::WaitableEvent::InitialState::NOT_SIGNALED);
+  // base::Unretained is safe because the class will be alive until
+  // |release_waiter| is signaled.

[mcasas, 2017/03/15 01:14:17]

I (still) think we need a comment here saying that
it's unsafe to just do a
  encoding_task_runner_->DeleteSoon(FROM_HERE, video_encoder_.release());
because |video_encoder_| holds a naked pointer to
us in |encoding_task_runner_|.

TODO+BUG point this situation out or not, I'll leave it
to you :-)
If VEA is staying alive in strange ways because of IPC,
mojo and its clear lifetime semantics can be of help
#justsayin'

[emircan, 2017/03/15 01:36:18]

Done.

   encoding_task_runner_->PostTask(
-      FROM_HERE, base::Bind(&media::VideoEncodeAccelerator::Destroy,
-                            base::Unretained(video_encoder_.release())));
+      FROM_HERE, base::Bind(&VEAEncoder::DestroyOnEncodingTaskRunner,
+                            base::Unretained(this), &release_waiter));
+  release_waiter.Wait();
 }
 
 void VEAEncoder::RequireBitstreamBuffers(unsigned int /*input_count*/,
@@ -744,10 +754,7 @@ void VEAEncoder::EncodeOnEncodingTaskRunner(
   frames_in_encode_.push(std::make_pair(
       media::WebmMuxer::VideoParameters(frame), capture_timestamp));
 
-  encoding_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&media::VideoEncodeAccelerator::Encode,
-                 base::Unretained(video_encoder_.get()), video_frame, false));
+  video_encoder_->Encode(video_frame, false);
 }
 
 void VEAEncoder::ConfigureEncoderOnEncodingTaskRunner(const gfx::Size& size) {
@@ -765,6 +772,14 @@ void VEAEncoder::ConfigureEncoderOnEncodingTaskRunner(const gfx::Size& size) {
   }
 }
 
+void VEAEncoder::DestroyOnEncodingTaskRunner(
+    base::WaitableEvent* async_waiter) {
+  DVLOG(3) << __func__;
+  DCHECK(encoding_task_runner_->BelongsToCurrentThread());

[mcasas, 2017/03/15 01:14:17]

This one as well.

[emircan, 2017/03/15 01:36:18]

Done.

+  video_encoder_.reset();
+  async_waiter->Signal();
+}
+
 // static
 void VpxEncoder::ShutdownEncoder(std::unique_ptr<base::Thread> encoding_thread,
                                  ScopedVpxCodecCtxPtr encoder) {