Implement ReadableStream as a V8 extra

Source/core/streams/ScriptQueuingStrategy.h

+#ifndef ScriptQueuingStrategy_h
+#define ScriptQueuingStrategy_h
+
+#include "bindings/core/v8/ScriptValue.h"
+#include "bindings/core/v8/ScriptWrappable.h"
+
+namespace blink {
+
+class CORE_EXPORT ScriptQueuingStrategy : public GarbageCollectedFinalized<ScriptQueuingStrategy>, public ScriptWrappable {
+    DEFINE_WRAPPERTYPEINFO();
+
+public:
+    explicit ScriptQueuingStrategy(double highWaterMark);
+    double highWaterMark();
+    virtual double size(ScriptValue chunk) = 0;
+
+    DECLARE_VIRTUAL_TRACE();
+
+private:
+    double m_highWaterMark;
+};
+
+} // namespace blink
+
+#endif ScriptQueuingStrategy_h