Clean forward declaration in public

public/platform/WebIDBKeyRange.h

 /*
  * Copyright (C) 2010 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
@@ skipping 15 matching lines @@
 #ifndef WebIDBKeyRange_h
 #define WebIDBKeyRange_h
 
 #include "WebCommon.h"
 #include "WebPrivatePtr.h"
 
 namespace blink {
 
 class IDBKeyRange;
 class WebIDBKey;
-class WebString;
 
 class WebIDBKeyRange {
 public:
     ~WebIDBKeyRange() { reset(); }
 
     WebIDBKeyRange(const WebIDBKeyRange& keyRange) { assign(keyRange); }
     WebIDBKeyRange(const WebIDBKey& lower, const WebIDBKey& upper, bool lowerOpen, bool upperOpen) { assign(lower, upper, lowerOpen, upperOpen); }
 
     BLINK_EXPORT WebIDBKey lower() const;
     BLINK_EXPORT WebIDBKey upper() const;
@@ skipping 10 matching lines @@
     operator IDBKeyRange*() const;
 #endif
 
 private:
     WebPrivatePtr<IDBKeyRange> m_private;
 };
 
 } // namespace blink
 
 #endif // WebIDBKeyRange_h