When performing a fast-path scroll, issue repaints for viewport-constrained layers

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 1401 matching lines @@
         }
 
         if (layer->hasAncestorWithFilterOutsets()) {
             // If the fixed layer has a blur/drop-shadow filter applied on at least one of its parents, we cannot
             // scroll using the fast path, otherwise the outsets of the filter will be moved around the page.
             return false;
         }
 
         IntRect updateRect = pixelSnappedIntRect(layer->repainter().repaintRectIncludingNonCompositingDescendants());
 
-        RenderLayer* enclosingCompositingLayer = layer->enclosingCompositingLayer(ExcludeSelf);
-        if (enclosingCompositingLayer && !enclosingCompositingLayer->renderer()->isRenderView()) {
+        const RenderLayerModelObject* repaintContainer = layer->renderer()->containerForRepaint();
+        if (repaintContainer && !repaintContainer->isRenderView()) {
             // If the fixed-position layer is contained by a composited layer that is not its containing block,
             // then we have to invalidate that enclosing layer, not the RenderView.
             // FIXME: Why do we need to issue this invalidation? Won't the fixed position element just scroll
             //        with the enclosing layer.
             updateRect.moveBy(scrollPosition());
             IntRect previousRect = updateRect;
             previousRect.move(scrollDelta);
             updateRect.unite(previousRect);
-            enclosingCompositingLayer->repainter().setBackingNeedsRepaintInRect(updateRect);
+            layer->renderer()->repaintUsingContainer(repaintContainer, updateRect, InvalidationScroll);
         } else {
             // Coalesce the paint invalidations that will be issued to the renderView.
             updateRect = contentsToRootView(updateRect);
             if (!isCompositedContentLayer && clipsPaintInvalidations())
                 updateRect.intersect(rectToScroll);
             if (!updateRect.isEmpty())
                 regionToUpdate.unite(updateRect);
         }
     }
 
@@ skipping 1830 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace WebCore