Adds OnClickCanceled callback to views::Button

ui/views/controls/button/button.h

Index: ui/views/controls/button/button.h
diff --git a/ui/views/controls/button/button.h b/ui/views/controls/button/button.h
index 84ca047b145c2fb26d65db01a8473cc36098de28..31c821d15b5cd8eeb679f6b955e33ba1150b8165 100644
--- a/ui/views/controls/button/button.h
+++ b/ui/views/controls/button/button.h
@@ -69,6 +69,11 @@ class VIEWS_EXPORT Button : public View {
   // Cause the button to notify the listener that a click occurred.
   virtual void NotifyClick(const ui::Event& event);
 
+  // Called when a button gets released without triggering an action.
+  // Note: This is only wired up for mouse button events and not gesture
+  // events.
+  virtual void OnClickCanceled(const ui::Event& event);
+
   // The button's listener. Notified when clicked.
   ButtonListener* listener_;