Have ScriptPromiseResolver on the Oilpan heap always.

Source/platform/CryptoResult.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 28 matching lines @@
 // Result cancellation status interface to allow non-Blink webcrypto threads
 // to query for status.
 class CryptoResultCancel : public ThreadSafeRefCounted<CryptoResultCancel> {
 public:
     virtual ~CryptoResultCancel() { }
 
     virtual bool cancelled() const = 0;
 };
 
 // Receives notification of completion of the crypto operation.
-class CryptoResult : public ThreadSafeRefCountedWillBeGarbageCollectedFinalized<CryptoResult> {
+class CryptoResult : public GarbageCollectedFinalized<CryptoResult> {
 public:
     virtual ~CryptoResult() { }
 
     virtual void completeWithError(WebCryptoErrorType, const WebString&) = 0;
     virtual void completeWithBuffer(const void* bytes, unsigned bytesSize) = 0;
     virtual void completeWithJson(const char* utf8Data, unsigned length) = 0;
     virtual void completeWithBoolean(bool) = 0;
     virtual void completeWithKey(const WebCryptoKey&) = 0;
     virtual void completeWithKeyPair(const WebCryptoKey& publicKey, const WebCryptoKey& privateKey) = 0;
 
     DEFINE_INLINE_VIRTUAL_TRACE() { }
 };
 
 } // namespace blink
 
 #endif // CryptoResult_h