Service Workers/Fetch: Fix Response constructor for empty/null

Source/modules/serviceworkers/Response.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 "Response.h"
 
 #include "bindings/core/v8/Dictionary.h"
 #include "bindings/core/v8/ExceptionState.h"
 #include "core/dom/DOMArrayBuffer.h"
@@ skipping 41 matching lines @@
     case WebServiceWorkerResponseTypeError:
         ASSERT(response->type() == FetchResponseData::ErrorType);
         break;
     }
 
     return response;
 }
 
 }
 
+Response* Response::create(ExecutionContext* context, ExceptionState& exceptionState)
+{
+    return create(context, nullptr, ResponseInit(), exceptionState);
+}
+
 Response* Response::create(ExecutionContext* context, Blob* body, const Dictionary& responseInit, ExceptionState& exceptionState)
 {
+    ASSERT(body);
     return create(context, body, ResponseInit(responseInit, exceptionState), exceptionState);
 }
 
 Response* Response::create(ExecutionContext* context, const String& body, const Dictionary& responseInit, ExceptionState& exceptionState)
 {
     OwnPtr<BlobData> blobData = BlobData::create();
     blobData->appendText(body, false);
     // "Set |Content-Type| to `text/plain;charset=UTF-8`."
     blobData->setContentType("text/plain;charset=UTF-8");
     const long long length = blobData->length();
@@ skipping 190 matching lines @@
 }
 
 void Response::trace(Visitor* visitor)
 {
     Body::trace(visitor);
     visitor->trace(m_response);
     visitor->trace(m_headers);
 }
 
 } // namespace blink