WebCrypto: Update the key usage names to reflect recent changes to the spec.

Source/modules/crypto/Key.h

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 30 matching lines @@
 
 class Algorithm;
 
 class Key : public ScriptWrappable, public RefCounted<Key> {
 public:
     static PassRefPtr<Key> create(const WebKit::WebCryptoKey& key) { return adoptRef(new Key(key)); }
 
     String type() const;
     bool extractable() const;
     Algorithm* algorithm();
-    Vector<String> keyUsage() const;
+    Vector<String> usages() const;
 
 protected:
     explicit Key(const WebKit::WebCryptoKey&);
 
     const WebKit::WebCryptoKey m_key;
     RefPtr<Algorithm> m_algorithm;
 };
 
 } // namespace WebCore
 
 #endif