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

Source/core/testing/Internals.h

Index: Source/core/testing/Internals.h
diff --git a/Source/core/testing/Internals.h b/Source/core/testing/Internals.h
index 0acaf35cc4fd9d11357f3f340bcb1c516211fcf3..46f797d8e40a7b14a7e118a5275b6491a2ab57a4 100644
--- a/Source/core/testing/Internals.h
+++ b/Source/core/testing/Internals.h
@@ -30,6 +30,7 @@
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
 #include "bindings/core/v8/Iterable.h"
 #include "bindings/core/v8/ScriptPromise.h"
+#include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/css/CSSComputedStyleDeclaration.h"
@@ -67,6 +68,7 @@ class Page;
 class PluginPlaceholderOptions;
 class PrivateScriptTest;
 class Range;
+class ReadableStream2;
 class SerializedScriptValue;
 class ShadowRoot;
 class TypeConversions;
@@ -78,7 +80,7 @@ class Internals final : public GarbageCollectedFinalized<Internals>, public Scri
     DEFINE_WRAPPERTYPEINFO();
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(Internals);
 public:
-    static Internals* create(Document*);
+    static Internals* create(ScriptState*);
     virtual ~Internals();
 
     static void resetToConsistentState(Page*);
@@ -360,8 +362,10 @@ public:
 
     ClientRectList* focusRingRects(Element*);
 
+    ScriptValue readableStream();
+
 private:
-    explicit Internals(Document*);
+    explicit Internals(ScriptState*);
     Document* contextDocument() const;
     LocalFrame* frame() const;
     Vector<String> iconURLs(Document*, int iconTypesMask) const;
@@ -371,6 +375,8 @@ private:
     Member<InternalRuntimeFlags> m_runtimeFlags;
 
     IterationSource* startIteration(ScriptState*, ExceptionState&) override;
+
+    ReadableStream2* m_readableStream;
 };
 
 } // namespace blink