[CSS Regions] Add new regionOversetChange event

Source/core/rendering/RenderRegion.h

Index: Source/core/rendering/RenderRegion.h
diff --git a/Source/core/rendering/RenderRegion.h b/Source/core/rendering/RenderRegion.h
index d06df36c186efd718c5cb70d20591e8b953625e0..5bf991d80752a941dbbc43801aebc25352c8cb32 100644
--- a/Source/core/rendering/RenderRegion.h
+++ b/Source/core/rendering/RenderRegion.h
@@ -82,15 +82,8 @@ public:
 
     void clearObjectStyleInRegion(const RenderObject*);
 
-    enum RegionState {
-        RegionUndefined,
-        RegionEmpty,
-        RegionFit,
-        RegionOverset
-    };
-
-    RegionState regionState() const { return isValid() ? m_regionState : RegionUndefined; }
-    void setRegionState(RegionState regionState) { m_regionState = regionState; }
+    RegionOversetState regionOversetState() const;
+    void setRegionOversetState(RegionOversetState);
     
     // These methods represent the width and height of a "page" and for a RenderRegion they are just the
     // content width and content height of a region. For RenderRegionSets, however, they will be the width and
@@ -197,7 +190,6 @@ private:
     bool m_isValid : 1;
     bool m_hasCustomRegionStyle : 1;
     bool m_hasAutoLogicalHeight : 1;
-    RegionState m_regionState;
 };
 
 inline RenderRegion* toRenderRegion(RenderObject* object)