Refactored static_cast'ing of events to use the AsXXXEvent() methods.

ui/events/event.h

Index: ui/events/event.h
diff --git a/ui/events/event.h b/ui/events/event.h
index 84305a70882abf28ed829d6b87340c3a4ab7aba3..4a1295772905999c48acbad986f076e8f7e110bd 100644
--- a/ui/events/event.h
+++ b/ui/events/event.h
@@ -30,6 +30,7 @@ class Transform;
 }
 
 namespace ui {
+class CancelModeEvent;
 class EventTarget;
 class KeyEvent;
 class LocatedEvent;
@@ -107,6 +108,10 @@ class EVENTS_EXPORT Event {
   bool IsAltGrDown() const { return (flags_ & EF_ALTGR_DOWN) != 0; }
   bool IsCapsLockOn() const { return (flags_ & EF_CAPS_LOCK_ON) != 0; }
 
+  bool IsCancelModeEvent() const {
+    return type_ == ET_CANCEL_MODE;
+  }
+
   bool IsKeyEvent() const {
     return type_ == ET_KEY_PRESSED || type_ == ET_KEY_RELEASED;
   }
@@ -220,6 +225,12 @@ class EVENTS_EXPORT Event {
            IsGestureEvent() || IsPointerEvent();
   }
 
+  // Convenience methods to cast |this| to a CancelModeEvent.
+  // IsCancelModeEvent() must be true as a precondition to calling these
+  // methods.
+  CancelModeEvent* AsCancelModeEvent();
+  const CancelModeEvent* AsCancelModeEvent() const;
+
   // Convenience methods to cast |this| to a GestureEvent. IsGestureEvent()
   // must be true as a precondition to calling these methods.
   GestureEvent* AsGestureEvent();