Set OnFramePresentedCB from main thread

Currently, we jump to the compositor thread in order to set the
new frame presented callback on the VideoFrameCompositor.

This CL is a small change that allows us to set that callback from the
main thread. This should help minimize the amount of frames we miss in
video.rAF calls.

Bug: 1012063
Change-Id: I521eb0bf0a6e71f59552c60276006e1884c1f989
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2040436
Commit-Queue: Thomas Guilbert <tguilbert@chromium.org>
Auto-Submit: Thomas Guilbert <tguilbert@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738770}

media/blink/video_frame_compositor.cc

@@ -261,7 +261,7 @@ void VideoFrameCompositor::SetOnNewProcessedFrameCallback(
 
 void VideoFrameCompositor::SetOnFramePresentedCallback(
     OnNewFramePresentedCB present_cb) {
-  DCHECK(task_runner_->BelongsToCurrentThread());
+  base::AutoLock lock(new_presented_frame_cb_lock_);
   new_presented_frame_cb_ = std::move(present_cb);
 }
 
@@ -284,8 +284,16 @@ bool VideoFrameCompositor::ProcessNewFrame(scoped_refptr<VideoFrame> frame,
   if (new_processed_frame_cb_)
     std::move(new_processed_frame_cb_).Run(tick_clock_->NowTicks());
 
-  if (new_presented_frame_cb_) {
-    std::move(new_presented_frame_cb_)
+  // Copy to a local variable to avoid potential deadlock when executing the
+  // callback.
+  OnNewFramePresentedCB frame_presented_cb;
+  {
+    base::AutoLock lock(new_presented_frame_cb_lock_);
+    frame_presented_cb = std::move(new_presented_frame_cb_);
+  }
+
+  if (frame_presented_cb) {
+    std::move(frame_presented_cb)
         .Run(GetCurrentFrame(), tick_clock_->NowTicks(), presentation_time,
              presentation_counter_);
   }

media/blink/video_frame_compositor.h

@@ -224,9 +224,13 @@ class MEDIA_BLINK_EXPORT VideoFrameCompositor : public VideoRendererSink,
 
   base::TimeTicks last_background_render_;
   OnNewProcessedFrameCB new_processed_frame_cb_;
-  OnNewFramePresentedCB new_presented_frame_cb_;
   cc::UpdateSubmissionStateCB update_submission_state_callback_;
 
+  // Callback used to satisfy video.rAF requests.
+  // Set on the main thread, fired on the compositor thread.
+  base::Lock new_presented_frame_cb_lock_;
+  OnNewFramePresentedCB new_presented_frame_cb_;
+
   // Set on the compositor thread, but also read on the media thread. Lock is
   // not used when reading |current_frame_| on the compositor thread.
   base::Lock current_frame_lock_;

media/blink/webmediaplayer_impl.cc

@@ -3332,13 +3332,8 @@ base::Optional<viz::SurfaceId> WebMediaPlayerImpl::GetSurfaceId() {
 }
 
 void WebMediaPlayerImpl::RequestAnimationFrame() {
-  vfc_task_runner_->PostTask(
-      FROM_HERE,
-      base::BindOnce(&VideoFrameCompositor::SetOnFramePresentedCallback,
-                     base::Unretained(compositor_.get()),
-                     BindToCurrentLoop(base::BindOnce(
-                         &WebMediaPlayerImpl::OnNewFramePresentedCallback,
-                         weak_factory_.GetWeakPtr()))));
+  compositor_->SetOnFramePresentedCallback(BindToCurrentLoop(base::BindOnce(
+      &WebMediaPlayerImpl::OnNewFramePresentedCallback, weak_this_)));
 }
 
 void WebMediaPlayerImpl::OnNewFramePresentedCallback(