[webcrypto] Remove the TODO for NullKey().

content/renderer/webcrypto/webcrypto_impl.h

 // Copyright (c) 2013 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 CONTENT_RENDERER_WEBCRYPTO_WEBCRYPTO_IMPL_H_
 #define CONTENT_RENDERER_WEBCRYPTO_WEBCRYPTO_IMPL_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "content/common/content_export.h"
@@ skipping 45 matching lines @@
   virtual void verifySignature(
       const WebKit::WebCryptoAlgorithm& algorithm,
       const WebKit::WebCryptoKey& key,
       const unsigned char* signature,
       unsigned signature_size,
       const unsigned char* data,
       unsigned data_size,
       WebKit::WebCryptoResult result);
 
   static void ShrinkBuffer(WebKit::WebArrayBuffer* buffer, unsigned new_size);
-  static WebKit::WebCryptoKey NullKey();
 
  protected:
   friend class WebCryptoImplTest;
 
   void Init();
 
   bool EncryptInternal(
       const WebKit::WebCryptoAlgorithm& algorithm,
       const WebKit::WebCryptoKey& key,
       const unsigned char* data,
@@ skipping 44 matching lines @@
       unsigned data_size,
       bool* signature_match);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(WebCryptoImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_WEBCRYPTO_WEBCRYPTO_IMPL_H_