[webcrypto] Make WebCryptoAlgorithm "nullable".

Source/core/platform/chromium/support/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 28 matching lines @@
 
 class WebCryptoKeyPrivate : public ThreadSafeRefCounted<WebCryptoKeyPrivate> {
 public:
     WebCryptoKeyPrivate(PassOwnPtr<WebCryptoKeyHandle> handle, WebCryptoKeyType type, bool extractable, const WebCryptoAlgorithm& algorithm, WebCryptoKeyUsageMask usages)
         : handle(handle)
         , type(type)
         , extractable(extractable)
         , algorithm(algorithm)
         , usages(usages)
     {
+        ASSERT(!algorithm.isNull());
     }
 
     const OwnPtr<WebCryptoKeyHandle> handle;
     const WebCryptoKeyType type;
     const bool extractable;
     const WebCryptoAlgorithm algorithm;
     const WebCryptoKeyUsageMask usages;
 };
 
 WebCryptoKey WebCryptoKey::create(WebCryptoKeyHandle* handle, WebCryptoKeyType type, bool extractable, const WebCryptoAlgorithm& algorithm, WebCryptoKeyUsageMask usages)
@@ skipping 32 matching lines @@
 {
     m_private = other.m_private;
 }
 
 void WebCryptoKey::reset()
 {
     m_private.reset();
 }
 
 } // namespace WebKit