Invalidate scrolling contents layer background when child invalidated.

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

Index: third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp b/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
index 81a301b5097852b9f51aed67aee644a216f7b286..b6f37938afaa291581f1b39c8c6ec9c6e9b7c34e 100644
--- a/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
+++ b/third_party/WebKit/Source/core/paint/ObjectPaintInvalidator.cpp
@@ -224,6 +224,9 @@ void ObjectPaintInvalidator::setBackingNeedsPaintInvalidationInRect(const Layout
         }
     } 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