[webcrypto] Add length parameter to HmacKeyAlgorithm. (blink)

Source/modules/crypto/HmacKeyAlgorithm.cpp

 /*
  * Copyright (C) 2014 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 @@
     return adoptRefWillBeNoop(new HmacKeyAlgorithm(algorithm));
 }
 
 KeyAlgorithm* HmacKeyAlgorithm::hash()
 {
     if (!m_hash)
         m_hash = KeyAlgorithm::createHash(m_algorithm.hmacParams()->hash());
     return m_hash.get();
 }
 
+unsigned HmacKeyAlgorithm::length()
+{
+    return m_algorithm.hmacParams()->lengthBits();
+}
+
 void HmacKeyAlgorithm::trace(Visitor* visitor)
 {
     KeyAlgorithm::trace(visitor);
     visitor->trace(m_hash);
 }
 
 HmacKeyAlgorithm::HmacKeyAlgorithm(const blink::WebCryptoKeyAlgorithm& algorithm)
     : KeyAlgorithm(algorithm)
 {
     ScriptWrappable::init(this);
 }
 
 } // namespace WebCore