Make CryptoResultImpl not to use WeakPtr.

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 59 matching lines @@
     // If called after completion (including cancellation) will return an empty
     // ScriptPromise.
     ScriptPromise promise();
 
 private:
     class WeakResolver;
     explicit CryptoResultImpl(ScriptState*);
 
     void cancel();
 
-    WeakPtr<ScriptPromiseResolver> m_resolver;
+    RefPtr<ScriptPromiseResolver> m_resolver;
     volatile int m_cancelled;
 };
 
 } // namespace blink
 
 #endif