Delay scrollContents until the next paint

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 482 matching lines @@
 
     if (renderer()->hasOverflowClip())
         flags |= HasSeenAncestorWithOverflowClip;
 
     if (flags & HasSeenViewportConstrainedAncestor
         || (flags & IsOverflowScroll && flags & HasSeenAncestorWithOverflowClip && !m_canSkipRepaintRectsUpdateOnScroll)) {
         // FIXME: Remove incremental compositing updates after fixing the chicken/egg issues
         // https://code.google.com/p/chromium/issues/detail?id=343756
         DisableCompositingQueryAsserts disabler;
         // FIXME: We could track the repaint container as we walk down the tree.
-        repainter().computeRepaintRects(renderer()->containerForRepaint(), geometryMap);
+        // repainter().computeRepaintRects(renderer()->containerForRepaint(), geometryMap);
+        // FIXME: This may cause extra repaints.
+        repainter().repaintIncludingNonCompositingDescendants(renderer()->containerForRepaint());

[abarth-chromium, 2014/03/08 06:54:52]

I'm not sure I understand what's changing here...

     } else {
         // Check that RenderLayerRepainter's cached rects are correct.
         // FIXME: re-enable these assertions when the issue with table cells is resolved: https://bugs.webkit.org/show_bug.cgi?id=103432
         // ASSERT(repainter().m_repaintRect == renderer()->clippedOverflowRectForRepaint(renderer()->containerForRepaint()));
         // ASSERT(repainter().m_outlineBox == renderer()->outlineBoundsForRepaint(renderer()->containerForRepaint(), geometryMap));
     }
 
     for (RenderLayer* child = firstChild(); child; child = child->nextSibling())
         child->updateLayerPositionsAfterScroll(geometryMap, flags);
 
@@ skipping 3517 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif