Incrementally build main thread scrolling reasons [spv2]

third_party/WebKit/Source/core/layout/LayoutObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1725 matching lines @@
 
   // Paint properties (see: |ObjectPaintProperties|) are built from an object's
   // state (location, transform, etc) as well as properties from ancestors.
   // When these inputs change, setNeedsPaintPropertyUpdate will cause a property
   // tree update during the next document lifecycle update.
   // TODO(pdr): Add additional granularity such as the ability to signal that
   // only a local paint property update is needed.
   void setNeedsPaintPropertyUpdate() {
     m_bitfields.setNeedsPaintPropertyUpdate(true);
   }
+  void setAllAncestorsNeedPaintPropertyUpdate() {
+    if (m_parent && !m_parent->needsPaintPropertyUpdate()) {
+      m_parent->setNeedsPaintPropertyUpdate();
+      m_parent->setAllAncestorsNeedPaintPropertyUpdate();
+    }
+  }
   void clearNeedsPaintPropertyUpdate() {
     DCHECK_EQ(document().lifecycle().state(), DocumentLifecycle::InPrePaint);
     m_bitfields.setNeedsPaintPropertyUpdate(false);
   }
   bool needsPaintPropertyUpdate() const {
     return m_bitfields.needsPaintPropertyUpdate();
   }
 
   void setIsScrollAnchorObject() { m_bitfields.setIsScrollAnchorObject(true); }
   // Clears the IsScrollAnchorObject bit if and only if no ScrollAnchors still
@@ skipping 886 matching lines @@
 CORE_EXPORT void showLineTree(const blink::LayoutObject*);
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showLayoutTree
 // can be called from gdb easily.
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1,
                                 const blink::LayoutObject* object2);
 
 #endif
 
 #endif  // LayoutObject_h