[Fetch] Support various operations after reading data partially.

Source/modules/serviceworkers/RespondWithObserver.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 "modules/serviceworkers/RespondWithObserver.h"
 
 #include "bindings/core/v8/ScriptFunction.h"
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptValue.h"
@@ skipping 185 matching lines @@
     if (responseType == FetchResponseData::OpaqueType && m_frameType != WebURLRequest::FrameTypeNone) {
         responseWasRejected();
         return;
     }
     if (response->bodyUsed()) {
         responseWasRejected();
         return;
     }
     response->setBodyUsed();
     if (BodyStreamBuffer* buffer = response->internalBuffer()) {
-        if (buffer == response->buffer() && response->streamAccessed()) {
-            bool dataLost = false;
-            buffer = response->createDrainingStream(&dataLost);
-            if (dataLost) {
-                executionContext()->addConsoleMessage(ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, "Returning the stream accessed Response to the page is not supported."));
-                responseWasRejected();
-                return;
-            }
-        }
+        if (buffer == response->buffer() && response->streamAccessed())
+            buffer = response->createDrainingStream();
         WebServiceWorkerResponse webResponse;
         response->populateWebServiceWorkerResponse(webResponse);
         RefPtrWillBeMember<Stream> outStream(Stream::create(executionContext(), ""));
         webResponse.setStreamURL(outStream->url());
         ServiceWorkerGlobalScopeClient::from(executionContext())->didHandleFetchEvent(m_eventID, webResponse);
         StreamUploader* uploader = new StreamUploader(buffer, outStream);
         uploader->start();
         m_state = Done;
         return;
     }
@@ skipping 11 matching lines @@
     , m_state(Initial)
 {
 }
 
 DEFINE_TRACE(RespondWithObserver)
 {
     ContextLifecycleObserver::trace(visitor);
 }
 
 } // namespace blink