Include viewport clip in visible rect of unclipped surfaces (2)

cc/trees/property_tree.cc

Index: cc/trees/property_tree.cc
diff --git a/cc/trees/property_tree.cc b/cc/trees/property_tree.cc
index 12aa51a5cabaff0bc300b696f10a5199c7d87090..d5277e80598b3f4608295262338738e07399f27c 100644
--- a/cc/trees/property_tree.cc
+++ b/cc/trees/property_tree.cc
@@ -1112,7 +1112,7 @@ void ClipTree::SetViewportClip(gfx::RectF viewport_rect) {
   set_needs_update(true);
 }
 
-gfx::RectF ClipTree::ViewportClip() {
+gfx::RectF ClipTree::ViewportClip() const {
   const unsigned long min_size = 1;
   DCHECK_GT(size(), min_size);
   return Node(kViewportNodeId)->clip;