Reland "media: Use BindOnce everywhere in GMBVFP."

Changes the use of Bind and Closure to BindOnce and OnceClosure in
GpuMemoryBufferVideoFramePool.

It additionally introduces a trampoline in MailboxHoldersReleased so
that if the callback is called on media_thread it can skip going trough
the message loop.
Previous the callback would be bound to the media_thread loop.

Two DCHECKs have also be added to check thread expectations.

TBR=dalecurtis, mcasas

Change-Id: I871e5505691b53a1871d2bd3e8a79ab1b75d2e69
Reviewed-on: https://chromium-review.googlesource.com/966583Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Commit-Queue: Daniele Castagna <dcastagna@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543727}

media/video/gpu_memory_buffer_video_frame_pool.cc

@@ -699,10 +699,9 @@ void GpuMemoryBufferVideoFramePool::PoolImpl::CopyVideoFrameToGpuMemoryBuffers(
       ++copies;
   }
 
-  const base::Closure copies_done =
-      base::Bind(&PoolImpl::OnCopiesDone, this, video_frame, frame_resources);
-  const base::RepeatingClosure barrier =
-      base::BarrierClosure(copies, copies_done);
+  const base::RepeatingClosure barrier = base::BarrierClosure(
+      copies, base::BindOnce(&PoolImpl::OnCopiesDone, this, video_frame,
+                             frame_resources));
 
   // Map the buffers.
   for (size_t i = 0; i < NumGpuMemoryBuffers(output_format_); i++) {
@@ -840,25 +839,24 @@ void GpuMemoryBufferVideoFramePool::PoolImpl::
   for (size_t i = 0; i < NumGpuMemoryBuffers(output_format_); i++)
     mailbox_holders[i].sync_token = sync_token;
 
-  auto release_mailbox_callback = BindToCurrentLoop(
-      base::Bind(&PoolImpl::MailboxHoldersReleased, this, frame_resources));
-
   VideoPixelFormat frame_format = VideoFormat(output_format_);
 
   // Create the VideoFrame backed by native textures.
   gfx::Size visible_size = video_frame->visible_rect().size();
   scoped_refptr<VideoFrame> frame = VideoFrame::WrapNativeTextures(
-      frame_format, mailbox_holders, release_mailbox_callback, coded_size,
+      frame_format, mailbox_holders, VideoFrame::ReleaseMailboxCB(), coded_size,
       gfx::Rect(visible_size), video_frame->natural_size(),
       video_frame->timestamp());
 
   if (!frame) {
     frame_resources->MarkUnused(tick_clock_->NowTicks());
-    release_mailbox_callback.Run(gpu::SyncToken());
+    MailboxHoldersReleased(frame_resources, gpu::SyncToken());
     std::move(frame_copy_requests_.front().frame_ready_cb).Run(video_frame);
     frame_copy_requests_.pop_front();
     return;
   }
+  frame->SetReleaseMailboxCB(
+      base::BindOnce(&PoolImpl::MailboxHoldersReleased, this, frame_resources));
 
   frame->set_color_space(video_frame->ColorSpace());
 
@@ -913,6 +911,7 @@ GpuMemoryBufferVideoFramePool::PoolImpl::~PoolImpl() {
 }
 
 void GpuMemoryBufferVideoFramePool::PoolImpl::Shutdown() {
+  DCHECK(media_task_runner_->BelongsToCurrentThread());
   // Clients don't care about copies once shutdown has started, so abort them.
   Abort();
 
@@ -941,6 +940,7 @@ GpuMemoryBufferVideoFramePool::PoolImpl::FrameResources*
 GpuMemoryBufferVideoFramePool::PoolImpl::GetOrCreateFrameResources(
     const gfx::Size& size,
     GpuVideoAcceleratorFactories::OutputFormat format) {
+  DCHECK(media_task_runner_->BelongsToCurrentThread());
 
   auto it = resources_pool_.begin();
   while (it != resources_pool_.end()) {
@@ -1019,7 +1019,13 @@ void GpuMemoryBufferVideoFramePool::PoolImpl::DeleteFrameResources(
 void GpuMemoryBufferVideoFramePool::PoolImpl::MailboxHoldersReleased(
     FrameResources* frame_resources,
     const gpu::SyncToken& release_sync_token) {
-  DCHECK(media_task_runner_->BelongsToCurrentThread());
+  if (!media_task_runner_->BelongsToCurrentThread()) {
+    media_task_runner_->PostTask(
+        FROM_HERE, base::BindOnce(&PoolImpl::MailboxHoldersReleased, this,
+                                  frame_resources, release_sync_token));
+    return;
+  }
+
   if (in_shutdown_) {
     DeleteFrameResources(gpu_factories_, frame_resources);
     delete frame_resources;