Make Response::body return v8-extra based stream behind flag

third_party/WebKit/Source/bindings/core/v8/V8HiddenValue.h

 // 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.
 
 #ifndef V8HiddenValue_h
 #define V8HiddenValue_h
 
 #include "bindings/core/v8/ScopedPersistent.h"
 #include "bindings/core/v8/ScriptPromiseProperties.h"
 #include "core/CoreExport.h"
@@ skipping 19 matching lines @@
     V(customElementTagName) \
     V(customElementType) \
     V(callback) \
     V(condition) \
     V(data) \
     V(detail) \
     V(document) \
     V(error) \
     V(event) \
     V(idbCursorRequest) \
+    V(internalBodyStream) \
     V(port1) \
     V(port2) \
     V(readableStreamReaderInResponse) \
     V(state) \
     V(stringData) \
     V(testInterfaces) \
     V(thenableHiddenPromise) \
     V(toStringString) \
     V(injectedScriptNative) \
     SCRIPT_PROMISE_PROPERTIES(V, Promise)  \
@@ skipping 18 matching lines @@
     V8HiddenValue() { }
 
 #define V8_DECLARE_FIELD(name) ScopedPersistent<v8::String> m_##name;
     V8_HIDDEN_VALUES(V8_DECLARE_FIELD);
 #undef V8_DECLARE_FIELD
 };
 
 } // namespace blink
 
 #endif // V8HiddenValue_h