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

third_party/WebKit/Source/core/dom/TouchInit.idl

Index: third_party/WebKit/Source/core/dom/TouchInit.idl
diff --git a/third_party/WebKit/Source/core/dom/TouchInit.idl b/third_party/WebKit/Source/core/dom/TouchInit.idl
index ba733b6f76bce06298896062b233c833a062bf50..345a896a385b33f4d275bf8d3bffe009d7b43a08 100644
--- a/third_party/WebKit/Source/core/dom/TouchInit.idl
+++ b/third_party/WebKit/Source/core/dom/TouchInit.idl
@@ -17,4 +17,10 @@ dictionary TouchInit {
              float       radiusY = 0;
              float       rotationAngle = 0;
              float       force = 0;
+
+             // Canvas HitRegion
+             // https://github.com/whatwg/html/issues/547
+             // TODO(zino): This attribute should be declared as partial dictionary but
+             // IDL parser can't support it yet. Please see: http://crbug.com/579896
+             DOMString? region = null;
 };