Enforce clearing renderers' paint invalidation state

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 1015 matching lines @@
     rootForPaintInvalidation->invalidateTreeIfNeeded(rootPaintInvalidationState);
 
     // Invalidate the paint of the frameviews scrollbars if needed
     if (hasVerticalBarDamage())
         invalidateRect(verticalBarDamage());
     if (hasHorizontalBarDamage())
         invalidateRect(horizontalBarDamage());
     resetScrollbarDamage();
 
     m_doFullPaintInvalidation = false;
+#ifndef NDEBUG
+    renderView()->assertSubtreeClearedPaintInvalidationState();
+#endif
 }
 
 DocumentLifecycle& FrameView::lifecycle() const
 {
     return m_frame->document()->lifecycle();
 }
 
 void FrameView::gatherDebugLayoutRects(RenderObject* layoutRoot)
 {
     bool isTracing;
@@ skipping 2242 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace blink