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

Source/core/streams/QueuingStrategyBase.h

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