LTHI's bg animation timer should set the fake thread to impl.

cc/layer_tree_host_impl.cc

 // Copyright 2011 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 "cc/layer_tree_host_impl.h"
 
 #include <algorithm>
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
@@ skipping 53 matching lines @@
         return make_scoped_ptr(new LayerTreeHostImplTimeSourceAdapter(layerTreeHostImpl, timeSource));
     }
     virtual ~LayerTreeHostImplTimeSourceAdapter()
     {
         m_timeSource->setClient(0);
         m_timeSource->setActive(false);
     }
 
     virtual void onTimerTick() OVERRIDE
     {
+        scoped_ptr<DebugScopedSetImplThread> setImplThread;

[enne (OOO), 2013/01/10 17:42:27]

I think this is the only conditional DebugScopedSetImplThread, so it really
needs a comment as to why this is ok.

+        if (!m_layerTreeHostImpl->proxy()->hasImplThread())
+            setImplThread.reset(new DebugScopedSetImplThread(m_layerTreeHostImpl->proxy()));
         m_layerTreeHostImpl->animate(base::TimeTicks::Now(), base::Time::Now());
     }
 
     void setActive(bool active)
     {
         if (active != m_timeSource->active())
             m_timeSource->setActive(active);
     }
 
 private:
@@ skipping 1547 matching lines @@
 }
 
 skia::RefPtr<SkPicture> LayerTreeHostImpl::capturePicture()
 {
     LayerTreeImpl* tree = pendingTree() ? pendingTree() : activeTree();
     LayerImpl* layer = getNonCompositedContentLayerRecursive(tree->RootLayer());
     return layer ? layer->getPicture() : skia::RefPtr<SkPicture>();
 }
 
 }  // namespace cc