Incrementally build main thread scrolling reasons [spv2]

third_party/WebKit/Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
    reserved.
 
    This library is free software; you can redistribute it and/or
@@ skipping 216 matching lines @@
     return m_viewportConstrainedObjects &&
            m_viewportConstrainedObjects->size() > 0;
   }
 
   // Objects with background-attachment:fixed.
   void addBackgroundAttachmentFixedObject(LayoutObject*);
   void removeBackgroundAttachmentFixedObject(LayoutObject*);
   bool hasBackgroundAttachmentFixedObjects() const {
     return m_backgroundAttachmentFixedObjects.size();
   }
+  bool hasBackgroundAttachmentFixedDescendants(const LayoutObject&) const;
   void invalidateBackgroundAttachmentFixedObjects();
 
   void handleLoadCompleted();
 
   void updateDocumentAnnotatedRegions() const;
 
   void didAttachDocument();
 
   void restoreScrollbar();
 
@@ skipping 901 matching lines @@
                   widget.isFrameView());
 DEFINE_TYPE_CASTS(FrameView,
                   ScrollableArea,
                   scrollableArea,
                   scrollableArea->isFrameView(),
                   scrollableArea.isFrameView());
 
 }  // namespace blink
 
 #endif  // FrameView_h