mac: Make the avatar button layer backed.

chrome/browser/ui/cocoa/profiles/avatar_button_controller.mm

 // Copyright 2014 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.
 
 #import "chrome/browser/ui/cocoa/profiles/avatar_button_controller.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/profiles/profiles_state.h"
 #include "chrome/browser/themes/theme_service.h"
@@ skipping 168 matching lines @@
     base::scoped_nsobject<CustomThemeButtonCell> cell(
         [[CustomThemeButtonCell alloc] initWithThemedWindow:isThemedWindow_]);
     SigninErrorController* errorController =
         profiles::GetSigninErrorController(browser->profile());
 
     [button_ setCell:cell.get()];
 
     if (errorController)
       [cell setHasError:errorController->HasError() withTitle:[button_ title]];
 
+    [button_ setWantsLayer:YES];
     [self setView:button_];
 
     [button_ setBezelStyle:NSShadowlessSquareBezelStyle];
     [button_ setButtonType:NSMomentaryChangeButton];
     [button_ setBordered:YES];
     // This is a workaround for an issue in the HoverImageButton where the
     // button is initially sized incorrectly unless a default image is provided.
     [button_ setImage:GetImageFromResourceID(IDR_AVATAR_MAC_BUTTON_DROPARROW)];
     [button_ setImagePosition:NSImageRight];
     [button_ setAutoresizingMask:NSViewMinXMargin | NSViewMinYMargin];
@@ skipping 72 matching lines @@
         layoutSubviews];
   }
 }
 
 - (void)updateErrorStatus:(BOOL)hasError {
   [[button_ cell] setHasError:hasError withTitle:[button_ title]];
   [self updateAvatarButtonAndLayoutParent:YES];
 }
 
 @end