Reuse submenu arrow images for trees (like the edit bookmark tree).

ui/native_theme/native_theme_mac.mm

 // Copyright (c) 2013 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.
 
 #include "ui/native_theme/native_theme_mac.h"
 
 #import <Cocoa/Cocoa.h>
 #include <stddef.h>
 
 #include "base/mac/mac_util.h"
@@ skipping 224 matching lines @@
     case kColorId_TreeSelectedText:
     case kColorId_TableSelectedText:
       return NSSystemColorToSkColor(
           [NSColor alternateSelectedControlTextColor]);
     case kColorId_TreeSelectionBackgroundFocused:
     case kColorId_TableSelectionBackgroundFocused:
       return NSSystemColorToSkColor([NSColor alternateSelectedControlColor]);
     case kColorId_TreeSelectionBackgroundUnfocused:
     case kColorId_TableSelectionBackgroundUnfocused:
       return kUnfocusedSelectedTextBackgroundColor;
-    case kColorId_TreeArrow:
     case kColorId_TableGroupingIndicatorColor:
       return SkColorSetRGB(140, 140, 140);
 
     default:
       // TODO(tapted): Handle all values and remove the default case.
       return GetAuraColor(color_id, this);
   }
 }
 
 void NativeThemeMac::PaintMenuPopupBackground(
@@ skipping 181 matching lines @@
   canvas->drawDRRect(outer_shape, shape, flags);
 }
 
 NativeThemeMac::NativeThemeMac() {
 }
 
 NativeThemeMac::~NativeThemeMac() {
 }
 
 }  // namespace ui