Clean up forward declarations in WebKit/Source

Source/core/css/CSSPathValue.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 CSSPathValue_h
 #define CSSPathValue_h
 
 #include "core/css/CSSValue.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
-class CSSPrimitiveValue;
-
 class CSSPathValue : public CSSValue {
 public:
     static PassRefPtrWillBeRawPtr<CSSPathValue> create(const String& pathString)
     {
         return adoptRefWillBeNoop(new CSSPathValue(pathString));
     }
 
     String customCSSText() const;
 
     bool equals(const CSSPathValue&) const;
 
     void traceAfterDispatch(Visitor*);
 
     const String& pathString() const { return m_pathString; }
 
 private:
     CSSPathValue(const String& pathString);
 
     String m_pathString;
 };
 
 DEFINE_CSS_VALUE_TYPE_CASTS(CSSPathValue, isPathValue());
 
 } // namespace blink
 
 #endif // CSSPathValue_h