Have ScriptPromiseResolver on the Oilpan heap always.

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 31 matching lines @@
 
 MODULES_EXPORT ExceptionCode webCryptoErrorToExceptionCode(WebCryptoErrorType);
 
 // Wrapper around a Promise to notify completion of the crypto operation.
 //
 // The thread on which CryptoResultImpl was created on is referred to as the
 // "origin thread".
 //
 //  * At creation time there must be an active ExecutionContext.
 //  * All methods of the CryptoResult implementation must be called from
-//    the origin thread. The exception is that ref(), deref(), and
-//    destruction may happen on another thread.
+//    the origin thread. The exception is that destruction may happen on
+//    another thread.
 //  * One of the completeWith***() functions must be called, or the
 //    m_resolver will be leaked until the ExecutionContext is destroyed.
 class CryptoResultImpl final : public CryptoResult {
 public:
-    static PassRefPtrWillBeRawPtr<CryptoResultImpl> create(ScriptState*);
+    static CryptoResultImpl* create(ScriptState*);
 
     ~CryptoResultImpl();
 
     void completeWithError(WebCryptoErrorType, const WebString&) override;
     void completeWithBuffer(const void* bytes, unsigned bytesSize) override;
     void completeWithJson(const char* utf8Data, unsigned length) override;
     void completeWithBoolean(bool) override;
     void completeWithKey(const WebCryptoKey&) override;
     void completeWithKeyPair(const WebCryptoKey& publicKey, const WebCryptoKey& privateKey) override;
 
@@ skipping 24 matching lines @@
         ResultCancel();
 
         int m_cancelled;
     };
 
     explicit CryptoResultImpl(ScriptState*);
 
     void cancel();
     void clearResolver();
 
-    RawPtrWillBeMember<Resolver> m_resolver;
+    Member<Resolver> m_resolver;
 
     // Separately communicate cancellation to WebCryptoResults so as to
     // allow this result object, which will be on the Oilpan heap, to be
     // GCed and destructed as needed. That is, it may end being GCed while
     // the thread owning the heap is detached and shut down, which will
     // in some cases happen before corresponding webcrypto operations have
     // all been processed. Hence these webcrypto operations cannot reliably
     // check cancellation status via this result object. So, keep a separate
     // cancellation status object for the purpose, which will outlive the
     // result object and can be safely accessed by multiple threads.
     RefPtr<ResultCancel> m_cancel;
 };
 
 } // namespace blink
 
 #endif // CryptoResultImpl_h