Use union type for NavigatorBeacon.sendBeacon()'s data argument

Source/core/loader/BeaconLoader.cpp

 // Copyright 2014 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 "core/loader/BeaconLoader.h"
 
 #include "core/FetchInitiatorTypeNames.h"
 #include "core/fetch/CrossOriginAccessControl.h"
 #include "core/fetch/FetchContext.h"
@@ skipping 87 matching lines @@
     AtomicString contentType;
     const String& blobType = data->type();
     if (!blobType.isEmpty() && isValidContentType(blobType))
         request.setHTTPContentType(AtomicString(contentType));
 
     issueRequest(frame, request);
     payloadLength = entitySize;
     return true;
 }
 
-bool BeaconLoader::sendBeacon(LocalFrame* frame, int allowance, const KURL& beaconURL, PassRefPtrWillBeRawPtr<DOMFormData>& data, int& payloadLength)
+bool BeaconLoader::sendBeacon(LocalFrame* frame, int allowance, const KURL& beaconURL, PassRefPtrWillBeRawPtr<DOMFormData> data, int& payloadLength)
 {
     ASSERT(data);
     ResourceRequest request(beaconURL);
     prepareRequest(frame, request);
 
     RefPtr<FormData> entityBody = data->createMultiPartFormData();
 
     unsigned long long entitySize = entityBody->sizeInBytes();
     if (allowance > 0 && static_cast<unsigned long long>(allowance) < entitySize)
         return false;
 
     AtomicString contentType = AtomicString("multipart/form-data; boundary=", AtomicString::ConstructFromLiteral) + entityBody->boundary().data();
     request.setHTTPBody(entityBody.release());
     request.setHTTPContentType(contentType);
 
     issueRequest(frame, request);
     payloadLength = entitySize;
     return true;
 }
 
 } // namespace blink