Implement ReadableStream as a V8 extra

Source/core/streams/ScriptReadableStream.cpp

+// 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.
+
+#include "config.h"
+#include "core/streams/ScriptReadableStream.h"
+
+#include "bindings/core/v8/ToV8.h"
+
+namespace blink {
+
+ScriptReadableStream::ScriptReadableStream(ScriptState* scriptState, ScriptUnderlyingSource* underlyingSource, ScriptQueuingStrategy* strategy)
+{
+    ScriptState::Scope scope(scriptState);
+
+    auto global = scriptState->context()->Global();
+    auto isolate = scriptState->isolate();
+
+    auto jsUnderlyingSource = toV8(underlyingSource, global, isolate);
+    auto jsStrategy = toV8(strategy, global, isolate);
+
+    auto sentinel = scriptState->getFromExtrasExports("createWithExternalControllerSentinel").v8Value();
+    auto constructor = scriptState->getFromExtrasExports("ReadableStream").v8Value().As<v8::Function>();
+
+    v8::Local<v8::Value> args[] = { jsUnderlyingSource, jsStrategy, sentinel };
+    auto jsStream = constructor->NewInstance(3, args);
+
+    m_stream = ScriptValue(scriptState, jsStream);
+}
+
+}