move KeyUsageAllows to more logical place(part1)

Source/platform/exported/WebCryptoKey.cpp

 /*
  * 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 87 matching lines @@
 {
     ASSERT(!isNull());
     return m_private->usages;
 }
 
 bool WebCryptoKey::isNull() const
 {
     return m_private.isNull();
 }
 
+bool WebCryptoKey::keyUsageAllows(const blink::WebCryptoKeyUsage usage) const
+{
+    return ((m_private->usages & usage) != 0);
+}
+
 void WebCryptoKey::assign(const WebCryptoKey& other)
 {
     m_private = other.m_private;
 }
 
 void WebCryptoKey::reset()
 {
     m_private.reset();
 }
 
 } // namespace blink