BytesConsumer::endRead can return Done

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 30 matching lines @@
 
     void onStateChange() override
     {
         bool destination1WasEmpty = m_destination1->isEmpty();
         bool destination2WasEmpty = m_destination2->isEmpty();
         bool hasEnqueued = false;
 
         while (true) {
             const char* buffer = nullptr;
             size_t available = 0;
-            switch (m_src->beginRead(&buffer, &available)) {
-            case Result::Ok: {
-                Chunk* chunk = new Chunk(buffer, available);
-                if (m_src->endRead(available) != Result::Ok) {
-                    clearAndNotify();
-                    return;
-                }
-                m_destination1->enqueue(chunk);
-                m_destination2->enqueue(chunk);
-                hasEnqueued = true;
-                break;
-            }
-            case Result::ShouldWait:
+            auto result = m_src->beginRead(&buffer, &available);
+            if (result == Result::ShouldWait) {
                 if (hasEnqueued && destination1WasEmpty)
                     m_destination1->notify();
                 if (hasEnqueued && destination2WasEmpty)
                     m_destination2->notify();
                 return;
+            }
+            Chunk* chunk = nullptr;
+            if (result == Result::Ok) {
+                chunk = new Chunk(buffer, available);
+                result = m_src->endRead(available);
+            }
+            switch (result) {
+            case Result::Ok:
+                DCHECK(chunk);
+                m_destination1->enqueue(chunk);
+                m_destination2->enqueue(chunk);
+                hasEnqueued = true;
+                break;
+            case Result::ShouldWait:
+                NOTREACHED();
+                return;
             case Result::Done:
                 if (destination1WasEmpty)
                     m_destination1->notify();
                 if (destination2WasEmpty)
                     m_destination2->notify();
                 return;
             case Result::Error:
                 clearAndNotify();
                 return;
             }
@@ skipping 245 matching lines @@
         *dest2 = new BytesConsumerForDataConsumerHandle(executionContext, FetchBlobDataConsumerHandle::create(executionContext, blobDataHandle));
         return;
     }
 
     Tee* tee = new Tee(executionContext, src);
     *dest1 = tee->destination1();
     *dest2 = tee->destination2();
 }
 
 } // namespace blink