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

Source/core/testing/ReadableStreamTestRequest.idl

Index: Source/core/testing/ReadableStreamTestRequest.idl
diff --git a/Source/core/html/canvas/WebGLVertexArrayObject.idl b/Source/core/testing/ReadableStreamTestRequest.idl
similarity index 51%
copy from Source/core/html/canvas/WebGLVertexArrayObject.idl
copy to Source/core/testing/ReadableStreamTestRequest.idl
index bb7ad2507cd2dcbefa8b3d68cff68418254ff4a2..7f739eaa711be820ccacc34c234d25aa5f1b8df0 100644
--- a/Source/core/html/canvas/WebGLVertexArrayObject.idl
+++ b/Source/core/testing/ReadableStreamTestRequest.idl
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-[
-    RuntimeEnabled=UnsafeES3APIs,
-    WillBeGarbageCollected
-] interface WebGLVertexArrayObject {
+[GarbageCollected]
+interface ReadableStreamTestRequest {
+    readonly attribute DOMString metadata;
+    [CallWith=ScriptState] readonly attribute object body;
 };