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"
+#include "core/CoreExport.h"
+#include "core/streams/UnderlyingSourceBase.h"
+#include <v8.h>
+
+namespace blink {
+
+// TODO probably needs to be GCed. Like ScriptPromiseProperty? Or we need a separate ReadableStreamProperty?
+
+class CORE_EXPORT ReadableStream2 {
+public:
+    enum State {
+        Readable = 0,
+        Closed = 1,
+        Errored = 2,
+    };
+
+    // This is for UA-created ReadableStreams
+    ReadableStream2(ScriptState*, UnderlyingSourceBase*, ScriptValue);
+
+    bool isLocked() const;
+
+    static ScriptValue createCountQueuingStrategy(ScriptState*, double highWaterMark);
+
+    // TODO(domenic): also a constructor for converting author-created ReadableStreams, e.g. for use in the bindings for
+    // functions/setters that accept ReadableStream?
+
+    bool isObject() const
+    {
+        return m_stream.isObject();
+    }
+
+    bool isNull() const
+    {
+        return m_stream.isNull();
+    }
+
+    bool isUndefinedOrNull() const
+    {
+        return m_stream.isUndefined() || m_stream.isNull();
+    }
+
+    ScriptValue scriptValue() const
+    {
+        return m_stream;
+    }
+
+    v8::Local<v8::Value> v8Value() const
+    {
+        return m_stream.v8Value();
+    }
+
+    v8::Isolate* isolate() const
+    {
+        return m_stream.isolate();
+    }
+
+    bool isEmpty() const
+    {
+        return m_stream.isEmpty();
+    }
+
+    void clear()
+    {
+        m_stream.clear();
+    }
+
+    bool operator==(const ReadableStream2& value) const
+    {
+        return m_stream == value.m_stream;
+    }
+
+    bool operator!=(const ReadableStream2& value) const
+    {
+        return !operator==(value);
+    }
+
+private:
+    ScriptValue m_stream;
+};
+
+} // namespace blink
+
+#endif // ReadableStream2_h