Enable DumpAccessibilityTree tests to use cross-process iframes.

third_party/WebKit/Source/modules/accessibility/AXScrollView.h

 /*
  * Copyright (C) 2011 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.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 26 matching lines @@
 
 class AXScrollView final : public AXObject {
 public:
     static AXScrollView* create(FrameView*, AXObjectCacheImpl&);
     AccessibilityRole roleValue() const override { return ScrollAreaRole; }
 
     ~AXScrollView() override;
     DECLARE_VIRTUAL_TRACE();
     void detach() override;
 
-protected:
-    ScrollableArea* getScrollableAreaIfScrollable() const override;
-
 private:
     AXScrollView(FrameView*, AXObjectCacheImpl&);
 
     bool computeAccessibilityIsIgnored(IgnoredReasons* = nullptr) const override;
     bool isAXScrollView() const override { return true; }
     bool isEnabled() const override { return true; }
 
     bool isAttachment() const override;
     Widget* widgetForAttachmentView() const override;
 
@@ skipping 17 matching lines @@
 
     RawPtrWillBeMember<FrameView> m_scrollView;
     Member<AXObject> m_horizontalScrollbar;
     Member<AXObject> m_verticalScrollbar;
     bool m_childrenDirty;
 };
 
 } // namespace blink
 
 #endif // AXScrollView_h