Move HoverButton and HoverImageButton from chrome/browser/ui/cocoa/ to ui/base/cocoa.

chrome/browser/ui/cocoa/hover_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 CHROME_BROWSER_UI_COCOA_HOVER_BUTTON_
-#define CHROME_BROWSER_UI_COCOA_HOVER_BUTTON_
-
-#import <Cocoa/Cocoa.h>
-
-#include "base/memory/scoped_nsobject.h"
-#import "ui/base/cocoa/tracking_area.h"
-
-// A button that changes when you hover over it and click it.
-@interface HoverButton : NSButton {
- @protected
-  // Enumeration of the hover states that the close button can be in at any one
-  // time. The button cannot be in more than one hover state at a time.
-  enum HoverState {
-    kHoverStateNone = 0,
-    kHoverStateMouseOver = 1,
-    kHoverStateMouseDown = 2
-  };
-
-  HoverState hoverState_;
-
- @private
-  // Tracking area for button mouseover states.
-  ui::ScopedCrTrackingArea trackingArea_;
-}
-
-@property(nonatomic) HoverState hoverState;
-
-// Enables or disables the tracking for the button.
-- (void)setTrackingEnabled:(BOOL)enabled;
-
-// Checks to see whether the mouse is in the button's bounds and update
-// the image in case it gets out of sync.  This occurs to the close button
-// when you close a tab so the tab to the left of it takes its place, and
-// drag the button without moving the mouse before you press the button down.
-- (void)checkImageState;
-
-@end
-
-#endif  // CHROME_BROWSER_UI_COCOA_HOVER_BUTTON_