Have ScriptPromiseResolver on the Oilpan heap always.

Source/modules/webusb/USB.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "modules/webusb/USB.h"
 
 #include "bindings/core/v8/CallbackPromiseAdapter.h"
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
@@ skipping 64 matching lines @@
     : m_controller(USBController::from(frame))
 {
 }
 
 ScriptPromise USB::getDevices(ScriptState* scriptState, const USBDeviceEnumerationOptions& options)
 {
     WebUSBClient* client = m_controller->client();
     if (!client)
         return ScriptPromise::rejectWithDOMException(scriptState, DOMException::create(NotSupportedError));
 
-    RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
 
     WebUSBDeviceEnumerationOptions webOptions;
     convertDeviceEnumerationOptions(options, &webOptions);
 
     // TODO(rockot): Re-enable this after CPA changes land.
     // That's https://codereview.chromium.org/1240763002/ and dependent patches.
     // client->getDevices(webOptions, new CallbackPromiseAdapter<DeviceArray, USBError>(resolver));
     ASSERT_NOT_REACHED();
 
     return promise;
 }
 
 DEFINE_TRACE(USB)
 {
     visitor->trace(m_controller);
 }
 
 } // namespace blink