CSSValue Immediates: Change CSSValue to an object instead of a pointer

Source/core/css/parser/CSSParserFastPaths.h

 // 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.
 
 #ifndef CSSParserFastPaths_h
 #define CSSParserFastPaths_h
 
 #include "core/CSSPropertyNames.h"
 #include "core/CSSValueKeywords.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
 
 namespace blink {
 
-class CSSValue;
+class NullableCSSValue;
 
 class CSSParserFastPaths {
 public:
     // Parses simple values like '10px' or 'green', but makes no guarantees
     // about handling any property completely.
-    static PassRefPtrWillBeRawPtr<CSSValue> maybeParseValue(CSSPropertyID, const String&, CSSParserMode);
+    static NullableCSSValue maybeParseValue(CSSPropertyID, const String&, CSSParserMode);
 
     // Properties handled here shouldn't be explicitly handled in CSSPropertyParser
     static bool isKeywordPropertyID(CSSPropertyID);
     static bool isValidKeywordPropertyAndValue(CSSPropertyID, CSSValueID);
 };
 
 } // namespace blink
 
 #endif // CSSParserFastPaths_h