Refactor wheel event handler registration in ScrollingCoordinator

Source/core/page/scrolling/ScrollingCoordinator.h

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 50 matching lines @@
     bool coordinatesScrollingForFrameView(FrameView*) const;
 
     // Called when any frame has done its layout.
     void notifyLayoutUpdated();
 
     // Should be called after compositing has been updated.
     void updateAfterCompositingChange();
 
     bool needsToUpdateAfterCompositingChange() const { return m_scrollGestureRegionIsDirty || m_touchEventTargetRectsAreDirty || frameViewIsDirty(); }
 
-    // Should be called whenever a wheel event handler is added or removed in the
-    // frame view's underlying document.
-    void frameViewWheelEventHandlerCountChanged(FrameView*);
+    // Should be called whenever the presence of wheel event handlers in the page changes.
+    void haveWheelEventHandlersChangedForPage();
+
+    // Should be called whenever the presence of scroll event handlers in the page changes.
+    void haveScrollEventHandlersChangedForPage();

[abarth-chromium, 2014/04/11 18:53:38]

I'd skip these comments.

didChangeScrollEventHandlers?

We generally use Objective-C style names for these sorts of notifications.  The
"ForPage" bit is redundant because ScrollingCoordinator is already a Page-level
object.

 
     // Should be called whenever the slow repaint objects counter changes between zero and one.
     void frameViewHasSlowRepaintObjectsDidChange(FrameView*);
 
     // Should be called whenever the set of fixed objects changes.
     void frameViewFixedObjectsDidChange(FrameView*);
 
     // Should be called whenever the root layer for the given frame view changes.
     void frameViewRootLayerDidChange(FrameView*);
 
@@ skipping 33 matching lines @@
 
     // For testing purposes only. This ScrollingCoordinator is reused between layout test, and must be reset
     // for the results to be valid.
     void reset();
 
 protected:
     explicit ScrollingCoordinator(Page*);
 
     bool isForMainFrame(ScrollableArea*) const;
 
-    unsigned computeCurrentWheelEventHandlerCount();
     GraphicsLayer* scrollLayerForFrameView(FrameView*);
     GraphicsLayer* counterScrollingLayerForFrameView(FrameView*);
 
     Page* m_page;
 
     // Dirty flags used to idenfity what really needs to be computed after compositing is updated.
     bool m_scrollGestureRegionIsDirty;
     bool m_touchEventTargetRectsAreDirty;
     bool m_shouldScrollOnMainThreadDirty;
 
 private:
-    void recomputeWheelEventHandlerCountForFrameView(FrameView*);
+    void updateHaveWheelEventHandlers();
+    void updateHaveScrollEventHandlers();
     void setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons);
 
     bool hasVisibleSlowRepaintViewportConstrainedObjects(FrameView*) const;
 
     bool touchHitTestingEnabled() const;
     void setShouldHandleScrollGestureOnMainThreadRegion(const Region&);
     void setTouchEventTargetRects(LayerHitTestRects&);
     void computeTouchEventTargetRects(LayerHitTestRects&);
-    void setWheelEventHandlerCount(unsigned);
 
     blink::WebScrollbarLayer* addWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation, PassOwnPtr<blink::WebScrollbarLayer>);
     blink::WebScrollbarLayer* getWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
     void removeWebScrollbarLayer(ScrollableArea*, ScrollbarOrientation);
 
     bool frameViewIsDirty() const;
 
     typedef HashMap<ScrollableArea*, OwnPtr<blink::WebScrollbarLayer> > ScrollbarMap;
     ScrollbarMap m_horizontalScrollbars;
     ScrollbarMap m_verticalScrollbars;
     HashSet<const RenderLayer*> m_layersWithTouchRects;
     bool m_wasFrameScrollable;
 
     // This is retained for testing.
     MainThreadScrollingReasons m_lastMainThreadScrollingReasons;
 };
 
 } // namespace WebCore
 
 #endif // ScrollingCoordinator_h