FrameView now notifies ScrollCoorinator of changes in its scrollable area set

Source/core/page/scrolling/ScrollingCoordinator.h

Index: Source/core/page/scrolling/ScrollingCoordinator.h
diff --git a/Source/core/page/scrolling/ScrollingCoordinator.h b/Source/core/page/scrolling/ScrollingCoordinator.h
index bf37a8aeac82f60af84953ad7a137406df268c2f..57cc22a46ab8668d93b84df4cd49d7fbce63076c 100644
--- a/Source/core/page/scrolling/ScrollingCoordinator.h
+++ b/Source/core/page/scrolling/ScrollingCoordinator.h
@@ -66,6 +66,9 @@ public:
     void updateHaveWheelEventHandlers();
     void updateHaveScrollEventHandlers();
 
+    // Should be called whenever scrollable area set changes.
+    void scrollableAreasDidChange();
+
     // Should be called whenever the slow repaint objects counter changes between zero and one.
     void frameViewHasSlowRepaintObjectsDidChange(FrameView*);