Adds OnClickCanceled callback to views::Button

ui/views/controls/button/button.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_CONTROLS_BUTTON_BUTTON_H_
 #define UI_VIEWS_CONTROLS_BUTTON_BUTTON_H_
 
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/view.h"
 
@@ skipping 51 matching lines @@
 
  protected:
   // Construct the Button with a Listener. The listener can be NULL. This can be
   // true of buttons that don't have a listener - e.g. menubuttons where there's
   // no default action and checkboxes.
   explicit Button(ButtonListener* listener);
 
   // 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.

[bruthig, 2015/10/22 15:18:50]

I think you should be explicit here about this only being called for mouse
releases and not gestures.  Either in the documentation of the method name.

Consider:

// Called when a button gets released without triggering an action.
// Note: This is only wired up for button releases caused by mouse
// button releases AND not gesture events.
virtual void NotifyMouseReleasedWithoutClick(const ui::Event& event);

[varkha, 2015/10/23 15:49:46]

Done.

+  virtual void NotifyReleasedWithoutClick(const ui::Event& event);
+
   // The button's listener. Notified when clicked.
   ButtonListener* listener_;
 
  private:
   // The text shown in a tooltip.
   base::string16 tooltip_text_;
 
   // Accessibility data.
   base::string16 accessible_name_;
 
   // The id tag associated with this button. Used to disambiguate buttons in
   // the ButtonListener implementation.
   int tag_;
 
   DISALLOW_COPY_AND_ASSIGN(Button);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_BUTTON_BUTTON_H_