[CSS Regions] Add new regionOversetChange event

Source/core/rendering/RenderNamedFlowThread.h

Index: Source/core/rendering/RenderNamedFlowThread.h
diff --git a/Source/core/rendering/RenderNamedFlowThread.h b/Source/core/rendering/RenderNamedFlowThread.h
index 67b6e95763e3cda87d5bf912ee47587a90188b8e..51f9f6fa9ebaa7a43bcf78a04bd2ce67cd5ebacc 100644
--- a/Source/core/rendering/RenderNamedFlowThread.h
+++ b/Source/core/rendering/RenderNamedFlowThread.h
@@ -87,6 +87,7 @@ private:
     virtual bool isChildAllowed(RenderObject*, RenderStyle*) const OVERRIDE;
 
     virtual void dispatchRegionLayoutUpdateEvent() OVERRIDE;
+    virtual void dispatchRegionOversetChangeEvent() OVERRIDE;
 
     bool dependsOn(RenderNamedFlowThread* otherRenderFlowThread) const;
     void addDependencyOnFlowThread(RenderNamedFlowThread*);
@@ -98,6 +99,7 @@ private:
 
     bool canBeDestroyed() const { return m_invalidRegionList.isEmpty() && m_regionList.isEmpty() && m_contentNodes.isEmpty(); }
     void regionLayoutUpdateEventTimerFired(Timer<RenderNamedFlowThread>*);
+    void regionOversetChangeEventTimerFired(Timer<RenderNamedFlowThread>*);
     void clearContentNodes();
 
 private:
@@ -123,6 +125,7 @@ private:
     RefPtr<NamedFlow> m_namedFlow;
 
     Timer<RenderNamedFlowThread> m_regionLayoutUpdateEventTimer;
+    Timer<RenderNamedFlowThread> m_regionOversetChangeEventTimer;
 };
 
 inline RenderNamedFlowThread* toRenderNamedFlowThread(RenderObject* object)