[cc] Fix crash when adding a child layer to its own parent.

cc/layer.cc

 // Copyright 2010 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 "config.h"
 
 #include "cc/layer.h"
 
 #include "cc/active_animation.h"
 #include "cc/animation_events.h"
@@ skipping 137 matching lines @@
     return false;
 }
 
 void Layer::addChild(scoped_refptr<Layer> child)
 {
     insertChild(child, numChildren());
 }
 
 void Layer::insertChild(scoped_refptr<Layer> child, size_t index)
 {
-    index = min(index, m_children.size());
     child->removeFromParent();
     child->setParent(this);
     child->m_stackingOrderChanged = true;
 
+    index = min(index, m_children.size());
     LayerList::iterator iter = m_children.begin();
     m_children.insert(iter + index, child);
     setNeedsCommit();
 }
 
 void Layer::removeFromParent()
 {
     if (m_parent)
         m_parent->removeChild(this);
 }
@@ skipping 678 matching lines @@
 {
     return 0;
 }
 
 void sortLayers(std::vector<scoped_refptr<Layer> >::iterator, std::vector<scoped_refptr<Layer> >::iterator, void*)
 {
     // Currently we don't use z-order to decide what to paint, so there's no need to actually sort Layers.
 }
 
 }  // namespace cc