Trivial: remove unused variable

Usage of compositor_task_runner has been moved to CreateSubmitter()

Change-Id: Iedd9eb118f0308ceb97a2857f32b6fed5b5b378c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1537568Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644792}

content/renderer/media/media_factory.cc

@@ -542,12 +542,6 @@ blink::WebMediaPlayer* MediaFactory::CreateWebMediaPlayerForMediaStream(
     const cc::LayerTreeSettings& settings) {
   RenderThreadImpl* const render_thread = RenderThreadImpl::current();
 
-  scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner =
-      render_thread->compositor_task_runner();
-  if (!compositor_task_runner.get())
-    compositor_task_runner =
-        render_frame_->GetTaskRunner(blink::TaskType::kInternalMediaRealTime);
-
   scoped_refptr<base::SingleThreadTaskRunner>
       video_frame_compositor_task_runner;
   std::unique_ptr<blink::WebVideoFrameSubmitter> submitter =