[Mac] Remove unused property on GradientButtonCell

chrome/browser/ui/cocoa/gradient_button_cell.h

Index: chrome/browser/ui/cocoa/gradient_button_cell.h
diff --git a/chrome/browser/ui/cocoa/gradient_button_cell.h b/chrome/browser/ui/cocoa/gradient_button_cell.h
index 882f14d215c06cd95a8280317019b9b0c0329eed..44ad719e9297b5947391aad880cf53eb0f88ae5b 100644
--- a/chrome/browser/ui/cocoa/gradient_button_cell.h
+++ b/chrome/browser/ui/cocoa/gradient_button_cell.h
@@ -64,7 +64,6 @@ typedef enum {
   base::scoped_nsobject<NSGradient> gradient_;
   gradient_button_cell::PulseState pulseState_;
   CGFloat outerStrokeAlphaMult_;  // For pulsing.
-  base::scoped_nsobject<NSImage> overlayImage_;
 }
 
 // Turn off theming.  Temporary work-around.
@@ -123,10 +122,6 @@ typedef enum {
 
 @property(assign, nonatomic) CGFloat hoverAlpha;
 
-// An image that will be drawn after the normal content of the button cell,
-// overlaying it.  Never themed.
-@property(retain, nonatomic) NSImage* overlayImage;
-
 @end
 
 @interface GradientButtonCell(TestingAPI)