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

Source/core/testing/Internals.cpp

Index: Source/core/testing/Internals.cpp
diff --git a/Source/core/testing/Internals.cpp b/Source/core/testing/Internals.cpp
index 9169dd89ec6d1691d33541d9a07fcff7313b8cab..55900addab992d2d0a0574df5a30b72dc80e0064 100644
--- a/Source/core/testing/Internals.cpp
+++ b/Source/core/testing/Internals.cpp
@@ -117,6 +117,9 @@
 #include "core/paint/DeprecatedPaintLayer.h"
 #include "core/plugins/testing/DictionaryPluginPlaceholder.h"
 #include "core/plugins/testing/DocumentFragmentPluginPlaceholder.h"
+#include "core/streams/ReadableStream2.h"
+#include "core/streams/ReadableStreamController.h"
+#include "core/streams/UnderlyingSourceBase.h"
 #include "core/svg/SVGImageElement.h"
 #include "core/testing/DictionaryTest.h"
 #include "core/testing/GCObservation.h"
@@ -126,6 +129,7 @@
 #include "core/testing/LayerRectList.h"
 #include "core/testing/PluginPlaceholderOptions.h"
 #include "core/testing/PrivateScriptTest.h"
+#include "core/testing/ReadableStreamTestCase.h"
 #include "core/testing/TypeConversions.h"
 #include "core/testing/UnionTypesTest.h"
 #include "core/workers/WorkerThread.h"
@@ -2451,4 +2455,9 @@ void Internals::setCapsLockState(bool enabled)
         PlatformKeyboardEvent::OverrideCapsLockState::On : PlatformKeyboardEvent::OverrideCapsLockState::Off);
 }
 
+ReadableStreamTestCase* Internals::createReadableStreamTestCase(ScriptState* scriptState)
+{
+    return new ReadableStreamTestCase(scriptState);
+}
+
 } // namespace blink