Use reference for FillLayer if possible

Source/core/rendering/RenderTheme.cpp

 /**
  * This file is part of the theme implementation for form controls in WebCore.
  *
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 539 matching lines @@
 {
     // There are more leaves than this, but we'll patch this function as we add support for
     // more controls.
     return appearance != CheckboxPart && appearance != RadioPart;
 }
 
 static bool isBackgroundOrBorderStyled(const RenderStyle& style, const CachedUAStyle& uaStyle)
 {
     // Code below excludes the background-repeat from comparison by resetting it
     FillLayer backgroundCopy = uaStyle.backgroundLayers;
-    FillLayer backgroundLayersCopy = *style.backgroundLayers();
+    FillLayer backgroundLayersCopy = style.backgroundLayers();
     backgroundCopy.setRepeatX(NoRepeatFill);
     backgroundCopy.setRepeatY(NoRepeatFill);
     backgroundLayersCopy.setRepeatX(NoRepeatFill);
     backgroundLayersCopy.setRepeatY(NoRepeatFill);
     // Test the style to see if the UA border and background match.
     return style.border() != uaStyle.border
         || backgroundLayersCopy != backgroundCopy
         || style.visitedDependentColor(CSSPropertyBackgroundColor) != uaStyle.backgroundColor;
 }
 
@@ skipping 647 matching lines @@
 
     // padding - not honored by WinIE, needs to be removed.
     style->resetPadding();
 
     // border - honored by WinIE, but looks terrible (just paints in the control box and turns off the Windows XP theme)
     // for now, we will not honor it.
     style->resetBorder();
 }
 
 } // namespace WebCore