cc : Fix bug in tree synchronization when mask layer changes

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index 35816ee56e78e1233886feb3d44afc1a628baf5d..f6c723cf2e82f1df13ec52518d5b5ac9acad8c06 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -416,8 +416,8 @@ void Layer::SetMaskLayer(Layer* mask_layer) {
   }
   mask_layer_ = mask_layer;
   if (mask_layer_.get()) {
-    DCHECK(!mask_layer_->parent());
     mask_layer_->RemoveFromParent();
+    DCHECK(!mask_layer_->parent());
     mask_layer_->SetParent(this);
     mask_layer_->SetIsMask(true);
   }