Implemented screen rotation animation experiment.

ui/compositor/layer_owner.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/layer_owner.h"
 
 #include "ui/compositor/layer_owner_delegate.h"
 
 namespace ui {
 
@@ skipping 54 matching lines @@
     ui::Layer* child = *it;
     new_layer->Add(child);
   }
 
   // Install the delegate last so that the delegate isn't notified as we copy
   // state to the new layer.
   new_layer->set_delegate(old_delegate);
 
   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();
 }
 
 void LayerOwner::DestroyLayer() {
   layer_ = NULL;
   layer_owner_.reset();
 }
 
 bool LayerOwner::OwnsLayer() const {
   return !!layer_owner_;
 }
 
 }  // namespace ui