Have ScriptPromiseResolver on the Oilpan heap always.

Source/modules/crypto/CryptoResultImpl.h

Index: Source/modules/crypto/CryptoResultImpl.h
diff --git a/Source/modules/crypto/CryptoResultImpl.h b/Source/modules/crypto/CryptoResultImpl.h
index b6cb6e90126c8290fdfbbd3a2172afc230868247..4517484e5548bfceb5d6a50c4b9fa09aa6d27a2b 100644
--- a/Source/modules/crypto/CryptoResultImpl.h
+++ b/Source/modules/crypto/CryptoResultImpl.h
@@ -55,9 +55,9 @@ MODULES_EXPORT ExceptionCode webCryptoErrorToExceptionCode(WebCryptoErrorType);
 //    m_resolver will be leaked until the ExecutionContext is destroyed.
 class CryptoResultImpl final : public CryptoResult {
 public:
-    ~CryptoResultImpl();
+    static CryptoResultImpl* create(ScriptState*);
 
-    static PassRefPtrWillBeRawPtr<CryptoResultImpl> create(ScriptState*);
+    ~CryptoResultImpl();
 
     void completeWithError(WebCryptoErrorType, const WebString&) override;
     void completeWithBuffer(const void* bytes, unsigned bytesSize) override;
@@ -71,6 +71,8 @@ public:
     // ScriptPromise.
     ScriptPromise promise();
 
+    DECLARE_VIRTUAL_TRACE();
+
 private:
     class Resolver;
     explicit CryptoResultImpl(ScriptState*);
@@ -78,9 +80,7 @@ private:
     void clearResolver();
     void cancel();
 
-    // FIXME: ScriptPromiseResolver should not be exported.
-    // Instead, use ScriptPromise.
-    ScriptPromiseResolver* m_resolver;
+    Member<Resolver> m_resolver;
     volatile int m_cancelled;
 };