Remove unused code from RenderThreadImpl::InitializeWebKit().

The removed code does not do anything useful -- it just churns the
reference counts and that's it.

Change-Id: I80ec8a5d559ae966038cf56d2e8606a0bb0f0201
Reviewed-on: https://chromium-review.googlesource.com/1104081Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Yuta Kitamura <yutak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568358}

content/renderer/render_thread_impl.cc

@@ -1259,12 +1259,6 @@ void RenderThreadImpl::InitializeWebKit(
   if (!command_line.HasSwitch(switches::kDisableThreadedCompositing))
     InitializeCompositorThread();
 
-  scoped_refptr<base::SingleThreadTaskRunner> compositor_impl_side_task_runner;
-  if (compositor_task_runner_)
-    compositor_impl_side_task_runner = compositor_task_runner_;
-  else
-    compositor_impl_side_task_runner = base::ThreadTaskRunnerHandle::Get();
-
   RenderThreadImpl::RegisterSchemes();
 
   RenderMediaClient::Initialize();