Hides ink ripple when a button drag is started

ui/views/controls/button/custom_button.h

 // Copyright (c) 2012 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_CUSTOM_BUTTON_H_
 #define UI_VIEWS_CONTROLS_BUTTON_CUSTOM_BUTTON_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "ui/events/event_constants.h"
 #include "ui/gfx/animation/animation_delegate.h"
@@ skipping 76 matching lines @@
   void OnMouseCaptureLost() override;
   void OnMouseEntered(const ui::MouseEvent& event) override;
   void OnMouseExited(const ui::MouseEvent& event) override;
   void OnMouseMoved(const ui::MouseEvent& event) override;
   bool OnKeyPressed(const ui::KeyEvent& event) override;
   bool OnKeyReleased(const ui::KeyEvent& event) override;
   void OnGestureEvent(ui::GestureEvent* event) override;
   bool AcceleratorPressed(const ui::Accelerator& accelerator) override;
   void ShowContextMenu(const gfx::Point& p,
                        ui::MenuSourceType source_type) override;
+  void OnDragStarted(const ui::LocatedEvent& event) override;
   void OnDragDone() override;
   void GetAccessibleState(ui::AXViewState* state) override;
   void VisibilityChanged(View* starting_from, bool is_visible) override;
 
   // Overridden from gfx::AnimationDelegate:
   void AnimationProgressed(const gfx::Animation* animation) override;
 
  protected:
   // Construct the Button with a Listener. See comment for Button's ctor.
   explicit CustomButton(ButtonListener* listener);
@@ skipping 59 matching lines @@
 
   // The event on which the button should notify its listener.
   NotifyAction notify_action_;
 
   DISALLOW_COPY_AND_ASSIGN(CustomButton);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_BUTTON_CUSTOM_BUTTON_H_