cc : Fix bug in tree synchronization when mask layer changes

cc/trees/tree_synchronizer.cc

Index: cc/trees/tree_synchronizer.cc
diff --git a/cc/trees/tree_synchronizer.cc b/cc/trees/tree_synchronizer.cc
index d50a57dbb676041d4b2aef4adf69026d9d5084f9..65096716a49dc3f8ec9dae3b2be7c31766d5da52 100644
--- a/cc/trees/tree_synchronizer.cc
+++ b/cc/trees/tree_synchronizer.cc
@@ -33,9 +33,9 @@ void SynchronizeTreesInternal(LayerType* layer_root, LayerTreeImpl* tree_impl) {
 
   for (auto& it : old_layer_map) {
     if (it.second) {
-      // Need to ensure that layer destruction doesn't tear down child
-      // LayerImpl that have been used in the new tree.
-      it.second->children().clear();
+      // Need to ensure that layer destruction doesn't tear down other layers
+      // linked to this LayerImpl that have been used in the new tree.
+      it.second->ClearLinksToOtherLayers();
     }
   }
 }