[Mac] Placate the stupid compiler.

chrome/browser/ui/cocoa/draggable_button_mixin.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 CHROME_BROWSER_UI_COCOA_DRAGGABLE_BUTTON_MIXIN_H_
 #define CHROME_BROWSER_UI_COCOA_DRAGGABLE_BUTTON_MIXIN_H_
 #pragma once
 
 #import <Cocoa/Cocoa.h>
 
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 // If it has a popup menu, for example, we want to perform the action on mouse
 // down, if possible (as long as user still gets chance to drag, if
 // appropriate).
 @property(nonatomic) BOOL actsOnMouseDown;
 
 // Designated initializer.
 - (id)initWithButton:(NSButton<DraggableButtonMixin>*)button;
 
 // NSResponder implementation. NSButton subclasses should invoke these methods
 // and only call super if the return value indicates such.
-- (DraggableButtonResult)mouseDown:(NSEvent*)event;
-- (DraggableButtonResult)mouseUp:(NSEvent*)event;
+- (DraggableButtonResult)mouseDownImpl:(NSEvent*)event;
+- (DraggableButtonResult)mouseUpImpl:(NSEvent*)event;
 
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_DRAGGABLE_BUTTON_MIXIN_H_