[Mac] Remove dead underlayImage_ from GradientButtonCell.

chrome/browser/cocoa/gradient_button_cell.h

Index: chrome/browser/cocoa/gradient_button_cell.h
diff --git a/chrome/browser/cocoa/gradient_button_cell.h b/chrome/browser/cocoa/gradient_button_cell.h
index fc79c09f32db486198bb32cc39b96f239d33ce59..a485f636e5987b606e32c521610257a55f63124b 100644
--- a/chrome/browser/cocoa/gradient_button_cell.h
+++ b/chrome/browser/cocoa/gradient_button_cell.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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.
 
@@ -37,7 +37,6 @@ typedef NSInteger ButtonType;
   CGFloat hoverAlpha_;  // 0-1. Controls the alpha during mouse hover
   NSTimeInterval lastHoverUpdate_;
   scoped_nsobject<NSGradient> gradient_;
-  scoped_nsobject<NSImage> underlayImage_;
 }
 
 // Turn off theming.  Temporary work-around.
@@ -53,10 +52,6 @@ typedef NSInteger ButtonType;
                         cellFrame:(NSRect)cellFrame
                   defaultGradient:(NSGradient*)defaultGradient;
 
-// An image to underlay beneath the existing image; not themed. May be nil.
-- (NSImage*)underlayImage;
-- (void)setUnderlayImage:(NSImage*)image;
-
 // Let the view know when the mouse moves in and out. A timer will update
 // the current hoverAlpha_ based on these events.
 - (void)setMouseInside:(BOOL)flag animate:(BOOL)animate;