Removing the assumption that child->SetParent will not change Drawability

cc/layers/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 "cc/layers/layer.h"
 
 #include <algorithm>
 
 #include "base/atomic_sequence_num.h"
 #include "base/debug/trace_event.h"
@@ skipping 229 matching lines @@
     replica_layer_->mask_layer_->reset_raster_scale_to_unknown();
 }
 
 void Layer::AddChild(scoped_refptr<Layer> child) {
   InsertChild(child, children_.size());
 }
 
 void Layer::InsertChild(scoped_refptr<Layer> child, size_t index) {
   DCHECK(IsPropertyChangeAllowed());
   child->RemoveFromParent();
+  AddDrawableDescendants(child->NumDescendantsThatDrawContent() +
+                         (child->DrawsContent() ? 1 : 0));
   child->SetParent(this);
   child->stacking_order_changed_ = true;
 
   index = std::min(index, children_.size());
   children_.insert(children_.begin() + index, child);
-  AddDrawableDescendants(child->NumDescendantsThatDrawContent() +
-                         (child->DrawsContent() ? 1 : 0));
   SetNeedsFullTreeSync();
 }
 
 void Layer::RemoveFromParent() {
   DCHECK(IsPropertyChangeAllowed());
   if (parent_)
     parent_->RemoveChildOrDependent(this);
 }
 
 void Layer::RemoveChildOrDependent(Layer* child) {
@@ skipping 969 matching lines @@
 
 void Layer::RunMicroBenchmark(MicroBenchmark* benchmark) {
   benchmark->RunOnLayer(this);
 }
 
 bool Layer::HasDelegatedContent() const {
   return false;
 }
 
 }  // namespace cc