Made ElementStyleResources store const CSSSVGDocumentValues

third_party/WebKit/Source/core/css/CSSSVGDocumentValue.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 23 matching lines @@
 
 class CSSSVGDocumentValue : public CSSValue {
 public:
     static CSSSVGDocumentValue* create(const String& url)
     {
         return new CSSSVGDocumentValue(url);
     }
     ~CSSSVGDocumentValue();
 
     DocumentResource* cachedSVGDocument() const { return m_document.get(); }
-    DocumentResource* load(Document*);
+    DocumentResource* load(Document*) const;
 
     String customCSSText() const;
     const String& url() const { return m_url; }
     bool loadRequested() const { return m_loadRequested; }
     bool equals(const CSSSVGDocumentValue&) const;
 
     DEFINE_INLINE_TRACE_AFTER_DISPATCH()
     {
         visitor->trace(m_document);
         CSSValue::traceAfterDispatch(visitor);
     }
 
 private:
     CSSSVGDocumentValue(const String& url);
 
     String m_url;
-    Member<DocumentResource> m_document;
-    bool m_loadRequested;
+
+    // Document cache.
+    mutable Member<DocumentResource> m_document;
+    mutable bool m_loadRequested;
 };
 
 DEFINE_CSS_VALUE_TYPE_CASTS(CSSSVGDocumentValue, isSVGDocumentValue());
 
 } // namespace blink
 
 #endif // CSSSVGDocumentValue_h