cc: Parameterize the main thread task runner

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index 3a2605b4c6800ffe6281ca95d956b8c96832ecb9..f6ed688d9b405aba456f7d12bea4dcc604afefbd 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -142,10 +142,15 @@ Compositor::Compositor(gfx::AcceleratedWidget widget,
         this,
         context_factory_->GetSharedBitmapManager(),
         settings,
+        base::MessageLoopProxy::current(),
         compositor_thread_loop_);
   } else {
     host_ = cc::LayerTreeHost::CreateSingleThreaded(
-        this, this, context_factory_->GetSharedBitmapManager(), settings);
+        this,
+        this,
+        context_factory_->GetSharedBitmapManager(),
+        settings,
+        base::MessageLoopProxy::current());
   }
   UMA_HISTOGRAM_TIMES("GPU.CreateBrowserCompositor",
                       base::TimeTicks::Now() - before_create);