Implement ReadableStream as a V8 extra

Source/core/streams/StreamTest.idl

Index: Source/core/streams/StreamTest.idl
diff --git a/Source/modules/app_banner/BeforeInstallPromptEventInit.idl b/Source/core/streams/StreamTest.idl
similarity index 62%
copy from Source/modules/app_banner/BeforeInstallPromptEventInit.idl
copy to Source/core/streams/StreamTest.idl
index fc66cc8d9a905f64723a05065d055c7281fae321..506171e17197238b86638dd0f284edda1bb25ae7 100644
--- a/Source/modules/app_banner/BeforeInstallPromptEventInit.idl
+++ b/Source/core/streams/StreamTest.idl
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-dictionary BeforeInstallPromptEventInit : EventInit {
-    sequence<DOMString> platforms;
+[GarbageCollected]
+interface StreamTest {
+    [CallWith=ScriptState] static ReadableStream2 test();
 };