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

Source/core/testing/Internals.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 49 matching lines @@
 class InternalRuntimeFlags;
 class InternalSettings;
 class Iterator;
 class LayerRectList;
 class LocalDOMWindow;
 class LocalFrame;
 class Node;
 class Page;
 class PluginPlaceholderOptions;
 class PrivateScriptTest;
+class ReadableStreamTestCase;
 class Range;
 class SerializedScriptValue;
 class ShadowRoot;
 class TypeConversions;
 class UnionTypesTest;
 template <typename NodeType> class StaticNodeTypeList;
 typedef StaticNodeTypeList<Node> StaticNodeList;
 
 class Internals final : public GarbageCollectedFinalized<Internals>, public ScriptWrappable, public ContextLifecycleObserver, public ValueIterable<int> {
     DEFINE_WRAPPERTYPEINFO();
@@ skipping 280 matching lines @@
     // |useCounterId| must be one of the values from the UseCounter::Feature enum.
     bool isUseCounted(Document*, int useCounterId);
 
     String unscopeableAttribute();
     String unscopeableMethod();
 
     ClientRectList* focusRingRects(Element*);
 
     void setCapsLockState(bool enabled);
 
+    ReadableStreamTestCase* createReadableStreamTestCase(ScriptState*);
+
 private:
     explicit Internals(ScriptState*);
+
     Document* contextDocument() const;
     LocalFrame* frame() const;
     Vector<String> iconURLs(Document*, int iconTypesMask) const;
     ClientRectList* annotatedRegions(Document*, bool draggable, ExceptionState&);
 
     DocumentMarker* markerAt(Node*, const String& markerType, unsigned index, ExceptionState&);
     Member<InternalRuntimeFlags> m_runtimeFlags;
 
     IterationSource* startIteration(ScriptState*, ExceptionState&) override;
 };
 
 } // namespace blink
 
 #endif // Internals_h