[webcrypto] Reject failed operations with a DOMException rather than null.

Source/modules/crypto/CryptoResultImpl.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 37 matching lines @@
 //  * The CryptoResult interface must only be called from the origin thread.
 //  * addref() and deref() can be called from any thread.
 //  * One of the completeWith***() functions must be called, or the
 //    PromiseState will be leaked until the ExecutionContext is destroyed.
 class CryptoResultImpl FINAL : public CryptoResult {
 public:
     ~CryptoResultImpl();
 
     static PassRefPtr<CryptoResultImpl> create();
 
-    virtual void completeWithError() OVERRIDE;
-    virtual void completeWithError(const blink::WebString&) OVERRIDE;
+    virtual void completeWithError(blink::WebCryptoErrorType, const blink::WebString&) OVERRIDE;
     virtual void completeWithBuffer(const blink::WebArrayBuffer&) OVERRIDE;
     virtual void completeWithBoolean(bool) OVERRIDE;
     virtual void completeWithKey(const blink::WebCryptoKey&) OVERRIDE;
     virtual void completeWithKeyPair(const blink::WebCryptoKey& publicKey, const blink::WebCryptoKey& privateKey) OVERRIDE;
 
     // It is only valid to call this before completion.
     ScriptPromise promise();
 
 private:
     explicit CryptoResultImpl(ExecutionContext*);
 
     class PromiseState;
     WeakPtr<PromiseState> m_promiseState;
 };
 
 } // namespace WebCore
 
 #endif