Implemented screen rotation animation experiment.

ui/compositor/layer_owner.cc

Index: ui/compositor/layer_owner.cc
diff --git a/ui/compositor/layer_owner.cc b/ui/compositor/layer_owner.cc
index cd614b37d8dca3e7e11326c2777d0e72cd80336d..9325d4a8dbd789c441f474df35291557f75d8917 100644
--- a/ui/compositor/layer_owner.cc
+++ b/ui/compositor/layer_owner.cc
@@ -73,6 +73,12 @@ scoped_ptr<Layer> LayerOwner::RecreateLayer() {
   if (layer_owner_delegate_)
     layer_owner_delegate_->OnLayerRecreated(old_layer.get(), new_layer);
 

[bruthig, 2015/03/06 16:00:33]

This file will NOT be submitted with this CL.  It is already in flight here:
https://codereview.chromium.org/983933002/ and is required by this CL.

+  // If old_layer was the layer tree root then we need to move the Compositor
+  // over to the new root.
+  const bool is_root = !old_layer->parent();
+  if (is_root && old_layer->GetCompositor())
+    old_layer->GetCompositor()->SetRootLayer(new_layer);
+
   return old_layer.Pass();
 }