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

Source/core/streams/QueuingStrategyBase.idl

+// 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.
+
+// This is not a spec interface. Instead, it is used to generate bindings
+// so that Blink code which wishes to create a stream can derive from
+// QueuingStrategyBase, and a JavaScript object can then be generated
+// automatically for use in initializing a ReadableStream.
+
+[NoInterfaceObject, GarbageCollected]
+interface QueuingStrategyBase {
+    readonly attribute double highWaterMark;
+    double size(any chunk);

[domenic, 2015/06/08 22:21:55]

This is broken right now, causing the layout tests to fail, since
EnqueueInReadableStream fails. I am not sure how to fix it.

The problem is that the stream spec is written to treat size as a function, not
a method. That is, it saves a copy `stream@[[strategySize]] = strategy.size` and
later calls it directly, with an undefined `this`. But all bindings-generated
methods check their `this`.

I am not sure how to do this best in Blink. Maybe queuing strategies should
always be implemented as V8 extras, and/or use one of the built-in ones
(ByteLengthQueuingStrategy/CountQueuingStrategy)? Or is there some way of making
our bindings not do the `this`-checking?

+};