Use const ref for LocalFrame::LocalFrameRoot and FrameTree::Top

third_party/WebKit/Source/core/layout/LayoutFrame.cpp

Index: third_party/WebKit/Source/core/layout/LayoutFrame.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutFrame.cpp b/third_party/WebKit/Source/core/layout/LayoutFrame.cpp
index 31cd2138448be9458c162b87dd80db27fc4a45ce..efc69ab45ff45e66f6baa4c411a07fa5577c2cda 100644
--- a/third_party/WebKit/Source/core/layout/LayoutFrame.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutFrame.cpp
@@ -49,7 +49,7 @@ void LayoutFrame::ImageChanged(WrappedImagePtr image, const IntRect*) {
           // main frame if there are no RemoteFrame ancestors in the frame tree.
           // Use of localFrameRoot() is discouraged but will change when cursor
           // update scheduling is moved from EventHandler to PageEventHandler.
-          frame->LocalFrameRoot()->GetEventHandler().ScheduleCursorUpdate();
+          frame->LocalFrameRoot().GetEventHandler().ScheduleCursorUpdate();
         }
       }
     }