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

third_party/WebKit/Source/modules/canvas2d/MouseEventHitRegion.cpp

Index: third_party/WebKit/Source/modules/canvas2d/MouseEventHitRegion.cpp
diff --git a/third_party/WebKit/Source/modules/canvas2d/MouseEventHitRegion.cpp b/third_party/WebKit/Source/modules/canvas2d/MouseEventHitRegion.cpp
index 71b628416551ee3daad5376353fa6165ad38da7b..49a83d72887bce93bfa2963774ca0d9027df8ed9 100644
--- a/third_party/WebKit/Source/modules/canvas2d/MouseEventHitRegion.cpp
+++ b/third_party/WebKit/Source/modules/canvas2d/MouseEventHitRegion.cpp
@@ -11,11 +11,7 @@ namespace blink {
 
 String MouseEventHitRegion::region(MouseEvent& event)
 {
-    if (!event.target() || !isHTMLCanvasElement(event.target()->toNode()))
-        return String();
-
-    HTMLCanvasElement* canvas = toHTMLCanvasElement(event.target()->toNode());
-    return regionIdFromAbsoluteLocation(*canvas, event.absoluteLocation());
+    return event.region();
 }
 
 } // namespace blink