Invalidate scrolling contents layer background when child invalidated.

third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp

 // Copyright 2016 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 "core/paint/ObjectPaintInvalidator.h"
 
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/layout/LayoutBlockFlow.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
@@ skipping 206 matching lines @@
     DCHECK(paintInvalidationContainer.compositingState() != NotComposited);
 
     PaintLayer& layer = *paintInvalidationContainer.layer();
     if (layer.groupedMapping()) {
         if (GraphicsLayer* squashingLayer = layer.groupedMapping()->squashingLayer()) {
             // Note: the subpixel accumulation of layer() does not need to be added here. It is already taken into account.
             squashingLayer->setNeedsDisplayInRect(enclosingIntRect(rect), reason, m_object);
         }
     } else if (m_object.compositedScrollsWithRespectTo(paintInvalidationContainer)) {
         layer.compositedLayerMapping()->setScrollingContentsNeedDisplayInRect(rect, reason, m_object);
+        if (paintInvalidationContainer.usesCompositedScrolling() && layer.compositedLayerMapping()->backgroundPaintsOntoScrollingContentsLayer()) {
+            invalidateDisplayItemClient(*layer.compositedLayerMapping()->scrollingContentsLayer(), reason);
+        }
     } else if (paintInvalidationContainer.usesCompositedScrolling()) {
         if (layer.compositedLayerMapping()->backgroundPaintsOntoScrollingContentsLayer()) {
             // TODO(flackr): Get a correct rect in the context of the scrolling contents layer to update
             // rather than updating the entire rect.
             const LayoutRect& scrollingContentsRect = toLayoutBox(m_object).layoutOverflowRect();
             layer.compositedLayerMapping()->setScrollingContentsNeedDisplayInRect(scrollingContentsRect, reason, m_object);
             layer.setNeedsRepaint();
             invalidateDisplayItemClient(*layer.compositedLayerMapping()->scrollingContentsLayer(), reason);
         }
         layer.compositedLayerMapping()->setNonScrollingContentsNeedDisplayInRect(rect, reason, m_object);
@@ skipping 234 matching lines @@
     m_object.invalidateDisplayItemClients(reason);
     return reason;
 }
 
 DisablePaintInvalidationStateAsserts::DisablePaintInvalidationStateAsserts()
     : m_disabler(&gDisablePaintInvalidationStateAsserts, true)
 {
 }
 
 } // namespace blink