Fix Compositing of Opaque Scrolling Layers and Add Tests

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 72cdc71f262586e46fe0df356fcf1e8ab8d21d7b..4c09ea2d7cd0f29fd919def67f8d4eb2be6578ef 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMapping.cpp
@@ -297,7 +297,7 @@ void CompositedLayerMapping::updateIsRootForIsolatedGroup()
 
 void CompositedLayerMapping::updateBackgroundPaintsOntoScrollingContentsLayer()
 {
-    bool shouldPaintOntoScrollingContentsLayer = shouldPaintBackgroundOntoScrollingContentsLayer();
+    bool shouldPaintOntoScrollingContentsLayer = m_owningLayer.shouldPaintBackgroundOntoScrollingContentsLayer();
     if (shouldPaintOntoScrollingContentsLayer != backgroundPaintsOntoScrollingContentsLayer()) {
         m_backgroundPaintsOntoScrollingContentsLayer = shouldPaintOntoScrollingContentsLayer;
         // If the background is no longer painted onto the scrolling contents
@@ -2582,14 +2582,6 @@ bool CompositedLayerMapping::invalidateLayerIfNoPrecedingEntry(size_t indexToCle
     return false;
 }
 
-bool CompositedLayerMapping::shouldPaintBackgroundOntoScrollingContentsLayer() const
-{
-    return !m_owningLayer.isRootLayer()
-        && m_owningLayer.scrollsOverflow()
-        && m_owningLayer.layoutObject()->style()->hasEntirelyLocalBackground()
-        && !m_owningLayer.stackingNode()->hasNegativeZOrderList();
-}
-
 bool CompositedLayerMapping::updateSquashingLayerAssignment(PaintLayer* squashedLayer, size_t nextSquashedLayerIndex)
 {
     GraphicsLayerPaintInfo paintInfo;