Fix issue when background changes painting target layer

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
index ebe400f573dabc4f76ab52aa00f487e94387c851..f3ff1558ea7f4d254c8a3eca5567aa9c2dfd59ca 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -368,11 +368,9 @@ void CompositedLayerMapping::
       backgroundPaintsOntoScrollingContentsLayer()) {
     m_backgroundPaintsOntoScrollingContentsLayer =
         shouldPaintOntoScrollingContentsLayer;
-    // If the background is no longer painted onto the scrolling contents layer
-    // the scrolling contents layer needs to be updated. If it is going to be
-    // painted onto the scrolling contents layer this update will be triggered
-    // by LayoutBoxModelObject::setBackingNeedsPaintInvalidationInRect
-    if (hasScrollingLayer() && !shouldPaintOntoScrollingContentsLayer)
+    // The scrolling contents layer needs to be updated for changed
+    // m_backgroundPaintsOntoScrollingContentsLayer.
+    if (hasScrollingLayer())
       m_scrollingContentsLayer->setNeedsDisplay();
   }
 }