Call VideoFrameProviderImpl::DidReceiveFrame when background render completes.

media/blink/video_frame_compositor.cc

 // Copyright 2014 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/blink/video_frame_compositor.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/default_tick_clock.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 201 matching lines @@
     opacity_changed_cb_.Run(IsOpaque(frame));
 
   current_frame_ = frame;
   return true;
 }
 
 void VideoFrameCompositor::BackgroundRender() {
   DCHECK(compositor_task_runner_->BelongsToCurrentThread());
   const base::TimeTicks now = tick_clock_->NowTicks();
   last_background_render_ = now;
-  CallRender(now, now + last_interval_, true);
+  bool new_frame = CallRender(now, now + last_interval_, true);
+  if (new_frame && client_)
+    client_->DidReceiveFrame();

[DaleCurtis, 2015/08/14 21:50:03]

Hmm, this means we're calling SetNeedsRedraw() even for occluded/invisible
frames -- which seemed wasteful and thus wasn't done here. Is that concern moot?
It is every 250ms, so I think it might be. 

[DaleCurtis, 2015/08/14 21:51:41]

Actually this can happen as frequently as every 4ms when slaved to WebGL.  See
http://ro.me/ where this might happen.

 }
 
 bool VideoFrameCompositor::CallRender(base::TimeTicks deadline_min,
                                       base::TimeTicks deadline_max,
                                       bool background_rendering) {
   DCHECK(compositor_task_runner_->BelongsToCurrentThread());
 
   base::AutoLock lock(lock_);
   if (!callback_) {
     // Even if we no longer have a callback, return true if we have a frame
@@ skipping 23 matching lines @@
   last_interval_ = deadline_max - deadline_min;
 
   // Restart the background rendering timer whether we're background rendering
   // or not; in either case we should wait for |kBackgroundRenderingTimeoutMs|.
   if (background_rendering_enabled_)
     background_rendering_timer_.Reset();
   return new_frame || had_new_background_frame;
 }
 
 }  // namespace media