Clean forward declaration in public

public/platform/WebFederatedCredential.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 WebFederatedCredential_h
 #define WebFederatedCredential_h
 
 #include "public/platform/WebCommon.h"
 #include "public/platform/WebCredential.h"
 #include "public/platform/WebString.h"
 #include "public/platform/WebURL.h"
 
 namespace blink {
 
-class PlatformFederatedCredential;
-
 class WebFederatedCredential : public WebCredential {
 public:
     BLINK_PLATFORM_EXPORT WebFederatedCredential(const WebString& id, const WebURL& federation, const WebString& name, const WebURL& avatarURL);
 
     // FIXME: Throw this away once it's unused on the chromium side.
     BLINK_PLATFORM_EXPORT WebFederatedCredential(const WebString& id, const WebString& name, const WebURL& avatarURL, const WebURL& federation);
 
     BLINK_PLATFORM_EXPORT void assign(const WebFederatedCredential&);
 
     BLINK_PLATFORM_EXPORT WebURL federation() const;
 
 #if INSIDE_BLINK
     BLINK_PLATFORM_EXPORT WebFederatedCredential(PlatformCredential*);
     BLINK_PLATFORM_EXPORT WebFederatedCredential& operator=(PlatformCredential*);
 #endif
 };
 
 } // namespace blink
 
 #endif // WebFederatedCredential_h