cc: Damage layer on delegated scroll

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 172e16f9ad3c88e85cd67a9cdb03954a91966f17..c23ea080aa055e1be7da5e045705a71108718519 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -928,6 +928,16 @@ void LayerTreeImpl::SetRootLayerScrollOffsetDelegate(
   }
 }
 
+void LayerTreeImpl::OnRootLayerDelegatedScrollOffsetChanged() {
+  DCHECK(root_layer_scroll_offset_delegate_);
+  if (inner_viewport_scroll_layer_) {
+    inner_viewport_scroll_layer_->DidScroll();
+  }
+  if (outer_viewport_scroll_layer_) {
+    outer_viewport_scroll_layer_->DidScroll();
+  }
+}
+
 void LayerTreeImpl::UpdateScrollOffsetDelegate() {
   DCHECK(InnerViewportScrollLayer());
   DCHECK(root_layer_scroll_offset_delegate_);