Change CSSImageValue's member variables from String to AtomicString

Source/core/css/CSSImageValue.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008 Apple Inc. All rights reserved.
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 16 matching lines @@
 #include "core/fetch/FetchRequest.h"
 #include "core/fetch/ImageResource.h"
 #include "core/loader/MixedContentChecker.h"
 #include "core/style/StyleFetchedImage.h"
 #include "core/style/StylePendingImage.h"
 #include "platform/weborigin/KURL.h"
 #include "platform/weborigin/SecurityPolicy.h"
 
 namespace blink {
 
-CSSImageValue::CSSImageValue(const String& rawValue, const KURL& url, StyleImage* image)
+CSSImageValue::CSSImageValue(const AtomicString& rawValue, const KURL& url, StyleImage* image)
     : CSSValue(ImageClass)
     , m_relativeURL(rawValue)
     , m_absoluteURL(url.string())
     , m_image(image)
     , m_accessedImage(image)
 {
 }
 
 CSSImageValue::~CSSImageValue()
 {
@@ skipping 70 matching lines @@
 
 DEFINE_TRACE_AFTER_DISPATCH(CSSImageValue)
 {
     visitor->trace(m_image);
     CSSValue::traceAfterDispatch(visitor);
 }
 
 void CSSImageValue::reResolveURL(const Document& document)
 {
     KURL url = document.completeURL(m_relativeURL);
-    if (url == m_absoluteURL)
+    AtomicString urlString(url.string());
+    if (urlString == m_absoluteURL)
         return;
-    m_absoluteURL = url.string();
+    m_absoluteURL = urlString;
     m_accessedImage = false;
     m_image.clear();
 }
 
 } // namespace blink