[Ash] Copy alpha_shape when recreating layers.

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 fc46d9f9d37e0d815c86d245480ae42afe2ee977..cd614b37d8dca3e7e11326c2777d0e72cd80336d 100644
--- a/ui/compositor/layer_owner.cc
+++ b/ui/compositor/layer_owner.cc
@@ -46,6 +46,9 @@ scoped_ptr<Layer> LayerOwner::RecreateLayer() {
   new_layer->SetFillsBoundsOpaquely(old_layer->fills_bounds_opaquely());
   new_layer->SetFillsBoundsCompletely(old_layer->FillsBoundsCompletely());
   new_layer->SetSubpixelPositionOffset(old_layer->subpixel_position_offset());
+  SkRegion* alpha_shape = old_layer->alpha_shape();
+  if (alpha_shape)
+    new_layer->SetAlphaShape(make_scoped_ptr(new SkRegion(*alpha_shape)));
 
   // Install new layer as a sibling of the old layer, stacked below it.
   if (old_layer->parent()) {