Remove the HasOwnBackingButPaintsIntoAncestor compositing state.

Source/core/rendering/RenderLayer.cpp

Index: Source/core/rendering/RenderLayer.cpp
diff --git a/Source/core/rendering/RenderLayer.cpp b/Source/core/rendering/RenderLayer.cpp
index df23cdb86160a149dd9a833c768252818adf277f..f491d16c428ffe6f534c135bce9d763d2795593b 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -652,7 +652,7 @@ void RenderLayer::updateScrollingStateAfterCompositingChange()
 
     m_hasNonCompositedChild = false;
     for (RenderLayer* child = firstChild(); child; child = child->nextSibling()) {
-        if (child->compositingState() == NotComposited || child->compositingState() == HasOwnBackingButPaintsIntoAncestor) {
+        if (child->compositingState() == NotComposited) {
             m_hasNonCompositedChild = true;
             return;
         }
@@ -2398,9 +2398,6 @@ CompositingState RenderLayer::compositingState() const
     if (!m_compositedLayerMapping)
         return NotComposited;
 
-    if (compositedLayerMapping()->paintsIntoCompositedAncestor())
-        return HasOwnBackingButPaintsIntoAncestor;
-
     return PaintsIntoOwnBacking;
 }