Change BodyStreamBuffer to be FetchDataConsumerHandle-based and enable backpressure in Fetch API

Source/modules/fetch/DataConsumerTee.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/fetch/DataConsumerTee.h"
 
 #include "core/dom/ActiveDOMObject.h"
 #include "core/dom/ExecutionContext.h"
+#include "modules/fetch/DataConsumerHandleUtil.h"
+#include "modules/fetch/FetchBlobDataConsumerHandle.h"
 #include "platform/Task.h"
 #include "platform/ThreadSafeFunctional.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebThread.h"
 #include "public/platform/WebTraceLocation.h"
 #include "wtf/Deque.h"
 #include "wtf/Functional.h"
 #include "wtf/ThreadSafeRefCounted.h"
 #include "wtf/ThreadingPrimitives.h"
@@ skipping 395 matching lines @@
     RefPtr<DestinationTracker> tracker = DestinationTracker::create(root);
     RefPtr<DestinationContext> context1 = DestinationContext::create();
     RefPtr<DestinationContext> context2 = DestinationContext::create();
 
     root->initialize(new SourceContext(root, src, context1, context2, executionContext));
 
     *dest1 = adoptPtr(new DestinationHandle(DestinationContext::Proxy::create(context1, tracker)));
     *dest2 = adoptPtr(new DestinationHandle(DestinationContext::Proxy::create(context2, tracker)));
 }
 
+void DataConsumerTee::create(ExecutionContext* executionContext, PassOwnPtr<FetchDataConsumerHandle> src, OwnPtr<FetchDataConsumerHandle>* dest1, OwnPtr<FetchDataConsumerHandle>* dest2)
+{
+    RefPtr<BlobDataHandle> blobDataHandle = src->obtainReader(nullptr)->drainAsBlobDataHandle(FetchDataConsumerHandle::Reader::AllowBlobWithInvalidSize);
+    if (blobDataHandle) {
+        *dest1 = FetchBlobDataConsumerHandle::create(executionContext, blobDataHandle);
+        *dest2 = FetchBlobDataConsumerHandle::create(executionContext, blobDataHandle);
+        return;
+    }
+
+    OwnPtr<WebDataConsumerHandle> webDest1, webDest2;
+    DataConsumerTee::create(executionContext, static_cast<PassOwnPtr<WebDataConsumerHandle>>(src), &webDest1, &webDest2);
+    *dest1 = createFetchDataConsumerHandleFromWebHandle(webDest1.release());
+    *dest2 = createFetchDataConsumerHandleFromWebHandle(webDest2.release());
+    return;
+}
+
 } // namespace blink