Don't cache subsequence whose layer is not fully contained by repaint rect

Source/core/paint/DeprecatedPaintLayerPainter.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/paint/DeprecatedPaintLayerPainter.h"
 
 #include "core/frame/Settings.h"
 #include "core/layout/ClipPathOperation.h"
 #include "core/layout/LayoutBlock.h"
@@ skipping 37 matching lines @@
     DeprecatedPaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), globalPaintFlags, LayoutSize(), paintingRoot);
     if (shouldPaintLayerInSoftwareMode(globalPaintFlags, paintFlags))
         paintLayer(context, paintingInfo, paintFlags);
 }
 
 static ShouldRespectOverflowClip shouldRespectOverflowClip(PaintLayerFlags paintFlags, const LayoutObject* layoutObject)
 {
     return (paintFlags & PaintLayerPaintingOverflowContents || (paintFlags & PaintLayerPaintingChildClippingMaskPhase && layoutObject->hasClipPath())) ? IgnoreOverflowClip : RespectOverflowClip;
 }
 
-void DeprecatedPaintLayerPainter::paintLayer(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
+DeprecatedPaintLayerPainter::PaintResult DeprecatedPaintLayerPainter::paintLayer(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
+{
+    PaintResult result = paintLayerInternal(context, paintingInfo, paintFlags);
+    m_paintLayer.clearNeedsRepaint();
+    return result;
+}
+
+DeprecatedPaintLayerPainter::PaintResult DeprecatedPaintLayerPainter::paintLayerInternal(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
 {
     // https://code.google.com/p/chromium/issues/detail?id=343772
     DisableCompositingQueryAsserts disabler;
 
     if (m_paintLayer.compositingState() != NotComposited) {
         if (paintingInfo.globalPaintFlags() & GlobalPaintFlattenCompositingLayers) {
             // FIXME: ok, but what about GlobalPaintFlattenCompositingLayers? That's for printing and drag-image.
             // FIXME: why isn't the code here global, as opposed to being set on each paintLayer() call?
             paintFlags |= PaintLayerUncachedClipRects;
         }
     }
 
     // Non self-painting leaf layers don't need to be painted as their layoutObject() should properly paint itself.
     if (!m_paintLayer.isSelfPaintingLayer() && !m_paintLayer.hasSelfPaintingLayerDescendant()) {
         ASSERT(!m_paintLayer.needsRepaint());
-        return;
+        return FullyPainted;
     }
 
-    bool needsRepaint = m_paintLayer.needsRepaint();
-    m_paintLayer.clearNeedsRepaint();
-
     if (shouldSuppressPaintingLayer(&m_paintLayer))
-        return;
+        return FullyPainted;
 
     // If this layer is totally invisible then there is nothing to paint.
     if (!m_paintLayer.layoutObject()->opacity() && !m_paintLayer.layoutObject()->hasBackdropFilter())
-        return;
-
-    if (!needsRepaint && SubsequenceRecorder::useCachedSubsequenceIfPossible(*context, m_paintLayer))
-        return;
-    SubsequenceRecorder subsequenceRecorder(*context, m_paintLayer);
+        return FullyPainted;
 
     if (m_paintLayer.paintsWithTransparency(paintingInfo.globalPaintFlags()))
         paintFlags |= PaintLayerHaveTransparency;
 
     LayerFixedPositionRecorder fixedPositionRecorder(*context, *m_paintLayer.layoutObject());
 
     // PaintLayerAppliedTransform is used in LayoutReplica, to avoid applying the transform twice.
-    if (m_paintLayer.paintsWithTransform(paintingInfo.globalPaintFlags()) && !(paintFlags & PaintLayerAppliedTransform)) {
-        paintLayerWithTransform(context, paintingInfo, paintFlags);
-        return;
-    }
+    if (m_paintLayer.paintsWithTransform(paintingInfo.globalPaintFlags()) && !(paintFlags & PaintLayerAppliedTransform))
+        return paintLayerWithTransform(context, paintingInfo, paintFlags);
 
-    paintLayerContentsAndReflection(context, paintingInfo, paintFlags);
+    return paintLayerContentsAndReflection(context, paintingInfo, paintFlags);
 }
 
-void DeprecatedPaintLayerPainter::paintLayerContentsAndReflection(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
+DeprecatedPaintLayerPainter::PaintResult DeprecatedPaintLayerPainter::paintLayerContentsAndReflection(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
 {
     ASSERT(m_paintLayer.isSelfPaintingLayer() || m_paintLayer.hasSelfPaintingLayerDescendant());
 
     PaintLayerFlags localPaintFlags = paintFlags & ~(PaintLayerAppliedTransform);
 
     // Paint the reflection first if we have one.
     if (m_paintLayer.reflectionInfo()) {
         ScopeRecorder scopeRecorder(*context);
         m_paintLayer.reflectionInfo()->paint(context, paintingInfo, localPaintFlags | PaintLayerPaintingReflection);
     }
 
     localPaintFlags |= PaintLayerPaintingCompositingAllPhases;
-    paintLayerContents(context, paintingInfo, localPaintFlags, fragmentPolicy);
+    return paintLayerContents(context, paintingInfo, localPaintFlags, fragmentPolicy);
 }
 
 class ClipPathHelper {
 public:
     ClipPathHelper(GraphicsContext* context, const DeprecatedPaintLayer& paintLayer, DeprecatedPaintLayerPaintingInfo& paintingInfo, LayoutRect& rootRelativeBounds, bool& rootRelativeBoundsComputed,
         const LayoutPoint& offsetFromRoot, PaintLayerFlags paintFlags)
         : m_resourceClipper(0), m_paintLayer(paintLayer), m_context(context)
     {
         const ComputedStyle& style = paintLayer.layoutObject()->styleRef();
 
@@ skipping 44 matching lines @@
             SVGClipPainter(*m_resourceClipper).finishEffect(*m_paintLayer.layoutObject(), m_context, m_clipperState);
     }
 private:
     LayoutSVGResourceClipper* m_resourceClipper;
     Optional<ClipPathRecorder> m_clipPathRecorder;
     SVGClipPainter::ClipperState m_clipperState;
     const DeprecatedPaintLayer& m_paintLayer;
     GraphicsContext* m_context;
 };
 
-void DeprecatedPaintLayerPainter::paintLayerContents(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfoArg, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
+DeprecatedPaintLayerPainter::PaintResult DeprecatedPaintLayerPainter::paintLayerContents(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfoArg, PaintLayerFlags paintFlags, FragmentPolicy fragmentPolicy)
 {
     ASSERT(m_paintLayer.isSelfPaintingLayer() || m_paintLayer.hasSelfPaintingLayerDescendant());
     ASSERT(!(paintFlags & PaintLayerAppliedTransform));
 
     bool isSelfPaintingLayer = m_paintLayer.isSelfPaintingLayer();
     bool isPaintingOverlayScrollbars = paintFlags & PaintLayerPaintingOverlayScrollbars;
     bool isPaintingScrollingContent = paintFlags & PaintLayerPaintingCompositingScrollingPhase;
     bool isPaintingCompositedForeground = paintFlags & PaintLayerPaintingCompositingForegroundPhase;
     bool isPaintingCompositedBackground = paintFlags & PaintLayerPaintingCompositingBackgroundPhase;
     bool isPaintingOverflowContents = paintFlags & PaintLayerPaintingOverflowContents;
     // Outline always needs to be painted even if we have no visible content. Also,
     // the outline is painted in the background phase during composited scrolling.
     // If it were painted in the foreground phase, it would move with the scrolled
     // content. When not composited scrolling, the outline is painted in the
     // foreground phase. Since scrolled contents are moved by paint invalidation in this
     // case, the outline won't get 'dragged along'.
     bool shouldPaintOutline = isSelfPaintingLayer && !isPaintingOverlayScrollbars
         && ((isPaintingScrollingContent && isPaintingCompositedBackground)
         || (!isPaintingScrollingContent && isPaintingCompositedForeground));
     bool shouldPaintContent = m_paintLayer.hasVisibleContent() && isSelfPaintingLayer && !isPaintingOverlayScrollbars;
 
+    bool needsRepaint = m_paintLayer.needsRepaint();
+    m_paintLayer.clearNeedsRepaint();
+
+    PaintResult result = FullyPainted;
+
     if (paintFlags & PaintLayerPaintingRootBackgroundOnly && !m_paintLayer.layoutObject()->isLayoutView() && !m_paintLayer.layoutObject()->isDocumentElement())
-        return;
+        return result;
+
+    Optional<SubsequenceRecorder> subsequenceRecorder;
+    if (isPaintingOverlayScrollbars) {
+        // We should have cleared the repaint flag in the first pass.
+        ASSERT(!needsRepaint);
+    } else {
+        if (!needsRepaint && SubsequenceRecorder::useCachedSubsequenceIfPossible(*context, m_paintLayer))
+            return result;
+        subsequenceRecorder.emplace(*context, m_paintLayer);
+    }
 
     DeprecatedPaintLayerPaintingInfo paintingInfo = paintingInfoArg;
 
     // Ensure our lists are up-to-date.
     m_paintLayer.stackingNode()->updateLayerListsIfNeeded();
 
     LayoutPoint offsetFromRoot;
     m_paintLayer.convertToLayerCoords(paintingInfo.rootLayer, offsetFromRoot);
 
     if (m_paintLayer.compositingState() == PaintsIntoOwnBacking)
         offsetFromRoot.move(m_paintLayer.subpixelAccumulation());
     else
         offsetFromRoot.move(paintingInfo.subPixelAccumulation);
 
+    LayoutRect bounds = m_paintLayer.physicalBoundingBox(offsetFromRoot);
+    if (!paintingInfo.paintDirtyRect.contains(bounds))
+        result = NotFullyPainted;
+
     LayoutRect rootRelativeBounds;
     bool rootRelativeBoundsComputed = false;
 
     if (paintingInfo.ancestorHasClipPathClipping && m_paintLayer.layoutObject()->style()->position() != StaticPosition)
         UseCounter::count(m_paintLayer.layoutObject()->document(), UseCounter::ClipPathOfPositionedElement);
 
     // These helpers output clip and compositing operations using a RAII pattern. Stack-allocated-varibles are destructed in the reverse order of construction,
     // so they are nested properly.
     ClipPathHelper clipPathHelper(context, m_paintLayer, paintingInfo, rootRelativeBounds, rootRelativeBoundsComputed, offsetFromRoot, paintFlags);
 
@@ skipping 43 matching lines @@
         bool shouldPaintNegZOrderList = (isPaintingScrollingContent && isPaintingOverflowContents) || (!isPaintingScrollingContent && isPaintingCompositedBackground);
         bool shouldPaintOwnContents = isPaintingCompositedForeground && shouldPaintContent;
         bool shouldPaintNormalFlowAndPosZOrderLists = isPaintingCompositedForeground;
         bool shouldPaintOverlayScrollbars = isPaintingOverlayScrollbars;
 
         if (shouldPaintBackground) {
             paintBackgroundForFragments(layerFragments, context, paintingInfo.paintDirtyRect,
                 localPaintingInfo, paintingRootForLayoutObject, paintFlags);
         }
 
-        if (shouldPaintNegZOrderList)
-            paintChildren(NegativeZOrderChildren, context, paintingInfo, paintFlags);
+        if (shouldPaintNegZOrderList) {
+            if (paintChildren(NegativeZOrderChildren, context, paintingInfo, paintFlags) == NotFullyPainted)
+                result = NotFullyPainted;
+        }
 
         if (shouldPaintOwnContents) {
             paintForegroundForFragments(layerFragments, context, paintingInfo.paintDirtyRect,
                 localPaintingInfo, paintingRootForLayoutObject, selectionOnly, paintFlags);
         }
 
         if (shouldPaintOutline)
             paintOutlineForFragments(layerFragments, context, localPaintingInfo, paintingRootForLayoutObject, paintFlags);
 
-        if (shouldPaintNormalFlowAndPosZOrderLists)
-            paintChildren(NormalFlowChildren | PositiveZOrderChildren, context, paintingInfo, paintFlags);
+        if (shouldPaintNormalFlowAndPosZOrderLists) {
+            if (paintChildren(NormalFlowChildren | PositiveZOrderChildren, context, paintingInfo, paintFlags) == NotFullyPainted)
+                result = NotFullyPainted;
+        }
 
         if (shouldPaintOverlayScrollbars)
             paintOverflowControlsForFragments(layerFragments, context, localPaintingInfo, paintFlags);
     } // FilterPainter block
 
     bool shouldPaintMask = (paintFlags & PaintLayerPaintingCompositingMaskPhase) && shouldPaintContent && m_paintLayer.layoutObject()->hasMask() && !selectionOnly;
     bool shouldPaintClippingMask = (paintFlags & PaintLayerPaintingChildClippingMaskPhase) && shouldPaintContent && !selectionOnly;
 
     if (shouldPaintMask)
         paintMaskForFragments(layerFragments, context, localPaintingInfo, paintingRootForLayoutObject, paintFlags);
     if (shouldPaintClippingMask) {
         // Paint the border radius mask for the fragments.
         paintChildClippingMaskForFragments(layerFragments, context, localPaintingInfo, paintingRootForLayoutObject, paintFlags);
     }
+
+    // Set subsequence not cacheable if the bounding box of this layer and descendants is not fully contained
+    // by paintRect, because later paintRect changes may expose new contents which will need repainting.
+    if (result == NotFullyPainted && subsequenceRecorder)
+        subsequenceRecorder->setUncacheable();
+
+    return result;
 }
 
 bool DeprecatedPaintLayerPainter::needsToClip(const DeprecatedPaintLayerPaintingInfo& localPaintingInfo, const ClipRect& clipRect)
 {
     return clipRect.rect() != localPaintingInfo.paintDirtyRect || clipRect.hasRadius();
 }
 
 bool DeprecatedPaintLayerPainter::atLeastOneFragmentIntersectsDamageRect(DeprecatedPaintLayerFragments& fragments, const DeprecatedPaintLayerPaintingInfo& localPaintingInfo, PaintLayerFlags localPaintFlags, const LayoutPoint& offsetFromRoot)
 {
     if (m_paintLayer.enclosingPaginationLayer())
         return true; // The fragments created have already been found to intersect with the damage rect.
 
     if (&m_paintLayer == localPaintingInfo.rootLayer && (localPaintFlags & PaintLayerPaintingOverflowContents))
         return true;
 
     for (DeprecatedPaintLayerFragment& fragment: fragments) {
         LayoutPoint newOffsetFromRoot = offsetFromRoot + fragment.paginationOffset;
         // Note that this really only works reliably on the first fragment. If the layer has visible
         // overflow and a subsequent fragment doesn't intersect with the border box of the layer
         // (i.e. only contains an overflow portion of the layer), intersection will fail. The reason
         // for this is that fragment.layerBounds is set to the border box, not the bounding box, of
         // the layer.
         if (m_paintLayer.intersectsDamageRect(fragment.layerBounds, fragment.backgroundRect.rect(), newOffsetFromRoot))
             return true;
     }
     return false;
 }
 
-void DeprecatedPaintLayerPainter::paintLayerWithTransform(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
+DeprecatedPaintLayerPainter::PaintResult DeprecatedPaintLayerPainter::paintLayerWithTransform(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
 {
     TransformationMatrix layerTransform = m_paintLayer.renderableTransform(paintingInfo.globalPaintFlags());
     // If the transform can't be inverted, then don't paint anything.
     if (!layerTransform.isInvertible())
-        return;
+        return FullyPainted;
 
     // FIXME: We should make sure that we don't walk past paintingInfo.rootLayer here.
     // m_paintLayer may be the "root", and then we should avoid looking at its parent.
     DeprecatedPaintLayer* parentLayer = m_paintLayer.parent();
 
     ClipRect ancestorBackgroundClipRect;
     if (parentLayer) {
         // Calculate the clip rectangle that the ancestors establish.
         ClipRectsContext clipRectsContext(paintingInfo.rootLayer, (paintFlags & PaintLayerUncachedClipRects) ? UncachedClipRects : PaintingClipRects, IgnoreOverlayScrollbarSize);
         if (shouldRespectOverflowClip(paintFlags, m_paintLayer.layoutObject()) == IgnoreOverflowClip)
@@ skipping 18 matching lines @@
         // We don't need to collect any fragments in the regular way here. We have already
         // calculated a clip rectangle for the ancestry if it was needed, and clipping this
         // layer is something that can be done further down the path, when the transform has
         // been applied.
         DeprecatedPaintLayerFragment fragment;
         fragment.backgroundRect = paintingInfo.paintDirtyRect;
         fragments.append(fragment);
     }
 
     bool needsScope = fragments.size() > 1;
+    PaintResult result = FullyPainted;
     for (const auto& fragment : fragments) {
         Optional<ScopeRecorder> scopeRecorder;
         if (needsScope)
             scopeRecorder.emplace(*context);
         Optional<LayerClipRecorder> clipRecorder;
         if (parentLayer) {
             ClipRect clipRectForFragment(ancestorBackgroundClipRect);
             clipRectForFragment.moveBy(fragment.paginationOffset);
             clipRectForFragment.intersect(fragment.backgroundRect);
             if (clipRectForFragment.isEmpty())
                 continue;
             if (needsToClip(paintingInfo, clipRectForFragment)) {
                 if (m_paintLayer.layoutObject()->style()->position() != StaticPosition && clipRectForFragment.isClippedByClipCss())
                     UseCounter::count(m_paintLayer.layoutObject()->document(), UseCounter::ClipCssOfPositionedElement);
                 clipRecorder.emplace(*context, *parentLayer->layoutObject(), DisplayItem::ClipLayerParent, clipRectForFragment, &paintingInfo, fragment.paginationOffset, paintFlags);
             }
         }
-
-        paintFragmentByApplyingTransform(context, paintingInfo, paintFlags, fragment.paginationOffset);
+        if (paintFragmentByApplyingTransform(context, paintingInfo, paintFlags, fragment.paginationOffset) == NotFullyPainted)
+            result = NotFullyPainted;
     }
+    return result;
 }
 
-void DeprecatedPaintLayerPainter::paintFragmentByApplyingTransform(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, const LayoutPoint& fragmentTranslation)
+DeprecatedPaintLayerPainter::PaintResult DeprecatedPaintLayerPainter::paintFragmentByApplyingTransform(GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags, const LayoutPoint& fragmentTranslation)
 {
     // This involves subtracting out the position of the layer in our current coordinate space, but preserving
     // the accumulated error for sub-pixel layout.
     LayoutPoint delta;
     m_paintLayer.convertToLayerCoords(paintingInfo.rootLayer, delta);
     delta.moveBy(fragmentTranslation);
     TransformationMatrix transform(m_paintLayer.renderableTransform(paintingInfo.globalPaintFlags()));
     IntPoint roundedDelta = roundedIntPoint(delta);
     transform.translateRight(roundedDelta.x(), roundedDelta.y());
     LayoutSize adjustedSubPixelAccumulation = paintingInfo.subPixelAccumulation + (delta - roundedDelta);
 
     Transform3DRecorder transform3DRecorder(*context, *m_paintLayer.layoutObject(), DisplayItem::Transform3DElementTransform, transform);
 
     // Now do a paint with the root layer shifted to be us.
     DeprecatedPaintLayerPaintingInfo transformedPaintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(transform.inverse().mapRect(paintingInfo.paintDirtyRect))), paintingInfo.globalPaintFlags(),
         adjustedSubPixelAccumulation, paintingInfo.paintingRoot);
     transformedPaintingInfo.ancestorHasClipPathClipping = paintingInfo.ancestorHasClipPathClipping;
-    paintLayerContentsAndReflection(context, transformedPaintingInfo, paintFlags, ForceSingleFragment);
+    return paintLayerContentsAndReflection(context, transformedPaintingInfo, paintFlags, ForceSingleFragment);
 }
 
-void DeprecatedPaintLayerPainter::paintChildren(unsigned childrenToVisit, GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
+DeprecatedPaintLayerPainter::PaintResult DeprecatedPaintLayerPainter::paintChildren(unsigned childrenToVisit, GraphicsContext* context, const DeprecatedPaintLayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
 {
+    PaintResult result = FullyPainted;
     if (!m_paintLayer.hasSelfPaintingLayerDescendant())
-        return;
+        return result;
 
 #if ENABLE(ASSERT)
     LayerListMutationDetector mutationChecker(m_paintLayer.stackingNode());
 #endif
 
     IntSize scrollOffsetAccumulation = paintingInfo.scrollOffsetAccumulation;
     if (m_paintLayer.layoutObject()->hasOverflowClip())
         scrollOffsetAccumulation += m_paintLayer.layoutBox()->scrolledContentOffset();
 
     DeprecatedPaintLayerStackingNodeIterator iterator(*m_paintLayer.stackingNode(), childrenToVisit);
     while (DeprecatedPaintLayerStackingNode* child = iterator.next()) {
         DeprecatedPaintLayerPainter childPainter(*child->layer());
         // If this Layer should paint into its own backing or a grouped backing, that will be done via CompositedDeprecatedPaintLayerMapping::paintContents()
         // and CompositedDeprecatedPaintLayerMapping::doPaintTask().
         if (!childPainter.shouldPaintLayerInSoftwareMode(paintingInfo.globalPaintFlags(), paintFlags))
             continue;
 
         DeprecatedPaintLayerPaintingInfo childPaintingInfo = paintingInfo;
         childPaintingInfo.scrollOffsetAccumulation = scrollOffsetAccumulation;
         // Rare case: accumulate scroll offset of non-stacking-context ancestors up to m_paintLayer.
         for (DeprecatedPaintLayer* parentLayer = child->layer()->parent(); parentLayer != &m_paintLayer; parentLayer = parentLayer->parent()) {
             if (parentLayer->layoutObject()->hasOverflowClip())
                 childPaintingInfo.scrollOffsetAccumulation += parentLayer->layoutBox()->scrolledContentOffset();
         }
 
-        childPainter.paintLayer(context, childPaintingInfo, paintFlags);
+        if (childPainter.paintLayer(context, childPaintingInfo, paintFlags) == NotFullyPainted)
+            result = NotFullyPainted;
     }
+    return result;
 }
 
 // FIXME: inline this.
 static bool paintForFixedRootBackground(const DeprecatedPaintLayer* layer, PaintLayerFlags paintFlags)
 {
     return layer->layoutObject()->isDocumentElement() && (paintFlags & PaintLayerPaintingRootBackgroundOnly);
 }
 
 bool DeprecatedPaintLayerPainter::shouldPaintLayerInSoftwareMode(const GlobalPaintFlags globalPaintFlags, PaintLayerFlags paintFlags)
 {
@@ skipping 154 matching lines @@
     if (!m_paintLayer.containsDirtyOverlayScrollbars())
         return;
 
     DeprecatedPaintLayerPaintingInfo paintingInfo(&m_paintLayer, LayoutRect(enclosingIntRect(damageRect)), paintFlags, LayoutSize(), paintingRoot);
     paintLayer(context, paintingInfo, PaintLayerPaintingOverlayScrollbars);
 
     m_paintLayer.setContainsDirtyOverlayScrollbars(false);
 }
 
 } // namespace blink