Pass approprite task runners to InterfacePtr::Bind via GpuVideoAcceleratorFactoriesImpl

This is part of efforts to replace base::ThreadTaskRunnerHandle::Get()
and SequencedTaskRunnerHandle::Get() with other appropriate task runners
in the renderer.

Bug: 786332
Change-Id: Idf6f5dd37a0c6d510a17a6f4c5546a86d9c07333
Reviewed-on: https://chromium-review.googlesource.com/983155Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Hajime Hoshi <hajimehoshi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550069}

content/renderer/media/gpu/gpu_video_accelerator_factories_impl.cc

@@ -375,7 +375,7 @@ void GpuVideoAcceleratorFactoriesImpl::
             unbound_vea_provider) {
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(!vea_provider_.is_bound());
-  vea_provider_.Bind(std::move(unbound_vea_provider));
+  vea_provider_.Bind(std::move(unbound_vea_provider), task_runner_);
 }
 
 void GpuVideoAcceleratorFactoriesImpl::ReleaseContextProvider() {