cc: Split out calcDrawEtc from drawLayers

cc/tree_synchronizer.cc

Index: cc/tree_synchronizer.cc
diff --git a/cc/tree_synchronizer.cc b/cc/tree_synchronizer.cc
index 8dd94d14ace1e0926fa516bd6438888b7c011c38..17f62002f018a793be85e496526c8c4a28d7b98e 100644
--- a/cc/tree_synchronizer.cc
+++ b/cc/tree_synchronizer.cc
@@ -62,6 +62,10 @@ scoped_ptr<LayerImpl> TreeSynchronizer::synchronizeTreeRecursive(RawPtrLayerImpl
 
     scoped_ptr<LayerImpl> layerImpl = reuseOrCreateLayerImpl(newLayers, oldLayers, layer);
 
+    // This call is not strictly necessary, but it prevents an extra tree
+    // recursion to set the host after synchronization in setRootLayer.
+    layerImpl->setLayerTreeHostImpl(hostImpl);
+
     layerImpl->clearChildList();
     const std::vector<scoped_refptr<Layer> >& children = layer->children();
     for (size_t i = 0; i < children.size(); ++i)
@@ -71,7 +75,6 @@ scoped_ptr<LayerImpl> TreeSynchronizer::synchronizeTreeRecursive(RawPtrLayerImpl
     layerImpl->setReplicaLayer(synchronizeTreeRecursive(newLayers, oldLayers, layer->replicaLayer(), hostImpl));
 
     layer->pushPropertiesTo(layerImpl.get());
-    layerImpl->setLayerTreeHostImpl(hostImpl);
 
     // Remove all dangling pointers. The pointers will be setup later in updateScrollbarLayerPointersRecursive phase
     if (ScrollbarAnimationController* scrollbarController = layerImpl->scrollbarAnimationController()) {