Fix BytesConsumer::read

third_party/WebKit/Source/modules/fetch/BytesConsumer.cpp

 // Copyright 2016 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 "modules/fetch/BytesConsumer.h"
 
 #include "core/dom/ExecutionContext.h"
 #include "core/dom/TaskRunnerHelper.h"
 #include "modules/fetch/BytesConsumerForDataConsumerHandle.h"
 #include "modules/fetch/FetchBlobDataConsumerHandle.h"
@@ skipping 305 matching lines @@
 BytesConsumer::Result BytesConsumer::read(char* buffer, size_t size, size_t* readSize)
 {
     *readSize = 0;
     const char* src = nullptr;
     size_t available;
     Result r = beginRead(&src, &available);
     if (r != Result::Ok)
         return r;
     *readSize = std::min(available, size);
     memcpy(buffer, src, *readSize);
-    return endRead(*readSize);
+    auto result = endRead(*readSize);
+    if (result != BytesConsumer::Result::Ok)
+        *readSize = 0;
+    return result;
 }
 
 void BytesConsumer::tee(ExecutionContext* executionContext, BytesConsumer* src, BytesConsumer** dest1, BytesConsumer** dest2)
 {
     RefPtr<BlobDataHandle> blobDataHandle = src->drainAsBlobDataHandle(BlobSizePolicy::AllowBlobWithInvalidSize);
     if (blobDataHandle) {
         // Register a client in order to be consistent.
         src->setClient(new NoopClient);
         // TODO(yhirano): Do not use FetchBlobDataConsumerHandle.
         *dest1 = new BytesConsumerForDataConsumerHandle(executionContext, FetchBlobDataConsumerHandle::create(executionContext, blobDataHandle));
         *dest2 = new BytesConsumerForDataConsumerHandle(executionContext, FetchBlobDataConsumerHandle::create(executionContext, blobDataHandle));
         return;
     }
 
     Tee* tee = new Tee(executionContext, src);
     *dest1 = tee->destination1();
     *dest2 = tee->destination2();
 }
 
 } // namespace blink