Add methods for creating V8 extras-based ReadableStreams from C++

Source/core/streams/ReadableStream2.h

+// 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.
+
+#ifndef ReadableStream2_h
+#define ReadableStream2_h
+
+#include "bindings/core/v8/ScriptState.h"
+#include "bindings/core/v8/ScriptValue.h"
+
+namespace blink {
+
+class UnderlyingSourceBase;
+
+namespace JSStreams {
+
+CORE_EXPORT ScriptValue createReadableStream(ScriptState*, UnderlyingSourceBase*, ScriptValue strategy);
+CORE_EXPORT ScriptValue createCountQueuingStrategy(ScriptState*, size_t highWaterMark);
+
+} // namespace JSStreams
+
+} // namespace blink
+
+#endif // ReadableStream2_h