Introduce ExclusiveStreamReader.

Source/modules/fetch/Body.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/fetch/Body.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
@@ skipping 95 matching lines @@
         ASSERT(m_state != BodyUsed);
         ASSERT(m_stream);
         ASSERT(dataLost);
         m_drainingStreamBuffer = new BodyStreamBuffer();
         if (m_state == Errored) {
             m_drainingStreamBuffer->error(exception());
             return m_drainingStreamBuffer;
         }
         // Take back the data in |m_stream|.
         Deque<std::pair<RefPtr<DOMArrayBuffer>, size_t>> tmp_queue;
-        if (m_stream->state() == ReadableStream::Readable)
-            m_stream->read(tmp_queue);
+        if (m_stream->stateInternal() == ReadableStream::Readable)
+            m_stream->readInternal(tmp_queue);
         *dataLost = m_queueCount != tmp_queue.size();
         while (!tmp_queue.isEmpty()) {
             std::pair<RefPtr<DOMArrayBuffer>, size_t> data = tmp_queue.takeFirst();
             m_drainingStreamBuffer->write(data.first);
         }
         if (m_state == Closed)
             m_drainingStreamBuffer->close();
         else
             m_stream->close();
         return m_drainingStreamBuffer;
@@ skipping 244 matching lines @@
 {
     // Canceling the load will call didFail which will remove the resolver.
     if (m_loader)
         m_loader->cancel();
 }
 
 bool Body::hasPendingActivity() const
 {
     if (m_resolver)
         return true;
-    if (m_stream && (m_stream->state() == ReadableStream::Readable || m_stream->state() == ReadableStream::Waiting))
+    if (m_stream && m_stream->hasPendingActivity())
         return true;
     return false;
 }
 
 void Body::trace(Visitor* visitor)
 {
     visitor->trace(m_resolver);
     visitor->trace(m_stream);
     visitor->trace(m_streamSource);
     ActiveDOMObject::trace(visitor);
@@ skipping 81 matching lines @@
 
 void Body::didBlobHandleReceiveError(PassRefPtrWillBeRawPtr<DOMException> exception)
 {
     if (!m_resolver)
         return;
     m_resolver->reject(exception);
     m_resolver.clear();
 }
 
 } // namespace blink