Canvas2d: Implement rerouting event by hit region's control.

third_party/WebKit/Source/core/events/MouseEvent.h

Index: third_party/WebKit/Source/core/events/MouseEvent.h
diff --git a/third_party/WebKit/Source/core/events/MouseEvent.h b/third_party/WebKit/Source/core/events/MouseEvent.h
index b3c5735cfc9b1313739347ceab34b6ec208c02ee..c999482fe5dfed5cd1aa5bfdf4c4247c051abc88 100644
--- a/third_party/WebKit/Source/core/events/MouseEvent.h
+++ b/third_party/WebKit/Source/core/events/MouseEvent.h
@@ -75,6 +75,8 @@ public:
     EventTarget* relatedTarget() const { return m_relatedTarget.get(); }
     void setRelatedTarget(PassRefPtrWillBeRawPtr<EventTarget> relatedTarget) { m_relatedTarget = relatedTarget; }
     PlatformMouseEvent::SyntheticEventType syntheticEventType() const { return m_syntheticEventType; }
+    const String& region() const { return m_region; }
+    void setRegion(const String& region) { m_region = region; }
 
     Node* toElement() const;
     Node* fromElement() const;
@@ -125,6 +127,7 @@ private:
     unsigned short m_buttons;
     RefPtrWillBeMember<EventTarget> m_relatedTarget;
     PlatformMouseEvent::SyntheticEventType m_syntheticEventType;
+    String m_region;
 };
 
 class MouseEventDispatchMediator final : public EventDispatchMediator {