cc: Parameterize the main thread task runner

ui/compositor/compositor.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 124 matching lines @@
 
   settings.impl_side_painting = IsUIImplSidePaintingEnabled();
   settings.use_zero_copy = IsUIZeroCopyEnabled();
 
   base::TimeTicks before_create = base::TimeTicks::Now();
   if (compositor_thread_loop_) {
     host_ = cc::LayerTreeHost::CreateThreaded(
         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);
   host_->SetRootLayer(root_web_layer_);
   host_->SetLayerTreeHostClientReady();
 }
 
 Compositor::~Compositor() {
   TRACE_EVENT0("shutdown", "Compositor::destructor");
 
@@ skipping 245 matching lines @@
     // CompositorObservers to be notified before starting another
     // draw cycle.
     ScheduleDraw();
   }
   FOR_EACH_OBSERVER(CompositorObserver,
                     observer_list_,
                     OnCompositingEnded(this));
 }
 
 }  // namespace ui