Reliably cancel in-progress CryptoResult(Impl) upon shutdown.

public/platform/WebCrypto.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 77 matching lines @@
     BLINK_PLATFORM_EXPORT void completeWithBoolean(bool);
     BLINK_PLATFORM_EXPORT void completeWithKey(const WebCryptoKey&);
     BLINK_PLATFORM_EXPORT void completeWithKeyPair(const WebCryptoKey& publicKey, const WebCryptoKey& privateKey);
 
     // Returns true if the underlying operation was cancelled.
     // This method can be called from any thread.
     BLINK_PLATFORM_EXPORT bool cancelled() const;
 
 #if INSIDE_BLINK
     BLINK_PLATFORM_EXPORT explicit WebCryptoResult(const PassRefPtrWillBeRawPtr<CryptoResult>&);
+
+    BLINK_PLATFORM_EXPORT void clear();
 #endif
 
 private:
     BLINK_PLATFORM_EXPORT void reset();
     BLINK_PLATFORM_EXPORT void assign(const WebCryptoResult&);
 
+    int m_cancelled;
+
     WebPrivatePtr<CryptoResult> m_impl;
 };
 
 class WebCryptoDigestor {
 public:
     virtual ~WebCryptoDigestor() { }
 
     // consume() will return |true| on the successful addition of data to the
     // partially generated digest. It will return |false| when that fails. After
     // a return of |false|, consume() should not be called again (nor should
@@ skipping 152 matching lines @@
     // Returns true on success.
     virtual bool serializeKeyForClone(const WebCryptoKey&, WebVector<unsigned char>&) { return false; }
 
 protected:
     virtual ~WebCrypto() { }
 };
 
 } // namespace blink
 
 #endif // WebCrypto_h