Clean up forward declarations in Source/core/frame

Source/core/frame/csp/CSPDirective.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 CSPDirective_h
 #define CSPDirective_h
 
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class ContentSecurityPolicy;
-class KURL;
 
 class CSPDirective {
     WTF_MAKE_NONCOPYABLE(CSPDirective);
 public:
     CSPDirective(const String& name, const String& value, ContentSecurityPolicy* policy)
         : m_name(name)
         , m_text(name + ' ' + value)
         , m_policy(policy)
     {
     }
 
     const String& text() const { return m_text; }
 
 protected:
     ContentSecurityPolicy* policy() const { return m_policy; }
 
 private:
     String m_name;
     String m_text;
     ContentSecurityPolicy* m_policy;
 };
 
 } // namespace blink
 
 #endif