Restore sanity to RenderLayerStackingNode::shouldBeNormalFlowOnly

Source/core/rendering/RenderLayerStackingNode.cpp

Index: Source/core/rendering/RenderLayerStackingNode.cpp
diff --git a/Source/core/rendering/RenderLayerStackingNode.cpp b/Source/core/rendering/RenderLayerStackingNode.cpp
index f335b4bd269a3342f9d6e2c878267c68c83608cc..a6ad456c69f5c955a97a3415e2faf3f584441177 100644
--- a/Source/core/rendering/RenderLayerStackingNode.cpp
+++ b/Source/core/rendering/RenderLayerStackingNode.cpp
@@ -56,8 +56,6 @@ namespace WebCore {
 // layer about some of its state.
 RenderLayerStackingNode::RenderLayerStackingNode(RenderLayer* layer)
     : m_layer(layer)
-    , m_descendantsAreContiguousInStackingOrder(false)
-    , m_descendantsAreContiguousInStackingOrderDirty(true)
     , m_normalFlowListDirty(true)
 #if !ASSERT_DISABLED
     , m_layerListMutationAllowed(true)
@@ -92,8 +90,7 @@ static inline bool compareZIndex(RenderLayerStackingNode* first, RenderLayerStac
 
 RenderLayerCompositor* RenderLayerStackingNode::compositor() const
 {
-    if (!renderer()->view())
-        return 0;
+    ASSERT(renderer()->view());
     return renderer()->view()->compositor();
 }
 
@@ -112,20 +109,13 @@ void RenderLayerStackingNode::dirtyZOrderLists()
         m_negZOrderList->clear();
     m_zOrderListsDirty = true;
 
-    m_descendantsAreContiguousInStackingOrderDirty = true;
-
     if (!renderer()->documentBeingDestroyed())
         compositor()->setCompositingLayersNeedRebuild();
 }
 
 void RenderLayerStackingNode::dirtyStackingContextZOrderLists()
 {
-    RenderLayerStackingNode* stackingContextNode = ancestorStackingContextNode();
-    if (stackingContextNode)
-        stackingContextNode->dirtyZOrderLists();
-
-    RenderLayerStackingNode* stackingNode = ancestorStackingNode();
-    if (stackingNode && stackingNode != stackingContextNode)
+    if (RenderLayerStackingNode* stackingNode = ancestorStackingContextNode())
         stackingNode->dirtyZOrderLists();
 }
 
@@ -141,9 +131,8 @@ void RenderLayerStackingNode::dirtyNormalFlowList()
         m_normalFlowList->clear();
     m_normalFlowListDirty = true;
 
-    if (!renderer()->documentBeingDestroyed()) {
+    if (!renderer()->documentBeingDestroyed())
         compositor()->setCompositingLayersNeedRebuild();
-    }
 }
 
 void RenderLayerStackingNode::rebuildZOrderLists()
@@ -303,7 +292,7 @@ void RenderLayerStackingNode::updateStackingNodesAfterStyleChange(const RenderSt
     EVisibility oldVisibility = oldStyle ? oldStyle->visibility() : VISIBLE;
     int oldZIndex = oldStyle ? oldStyle->zIndex() : 0;
 
-    // FIXME: RenderLayer already handles visibility changes through our visiblity dirty bits. This logic could
+    // FIXME: RenderLayer already handles visibility changes through our visibility dirty bits. This logic could
     // likely be folded along with the rest.
     bool isStackingContext = this->isStackingContext();
     if (isStackingContext == wasStackingContext && oldVisibility == renderer()->style()->visibility() && oldZIndex == zIndex())
@@ -319,22 +308,7 @@ void RenderLayerStackingNode::updateStackingNodesAfterStyleChange(const RenderSt
 
 bool RenderLayerStackingNode::shouldBeNormalFlowOnly() const
 {
-    const bool couldBeNormalFlow = renderer()->hasOverflowClip()
-        || renderer()->hasReflection()
-        || renderer()->hasMask()
-        || renderer()->isCanvas()
-        || renderer()->isVideo()
-        || renderer()->isEmbeddedObject()
-        || renderer()->isRenderIFrame()
-        || (renderer()->style()->specifiesColumns() && !layer()->isRootLayer());
-    const bool preventsElementFromBeingNormalFlow = renderer()->isPositioned()
-        || renderer()->hasTransform()
-        || renderer()->hasClipPath()
-        || renderer()->hasFilter()
-        || renderer()->hasBlendMode()
-        || layer()->isTransparent();
-
-    return couldBeNormalFlow && !preventsElementFromBeingNormalFlow;
+    return !isStackingContext() && !renderer()->isPositioned();
 }
 
 void RenderLayerStackingNode::updateIsNormalFlowOnly()
@@ -351,21 +325,11 @@ void RenderLayerStackingNode::updateIsNormalFlowOnly()
 
 RenderLayerStackingNode* RenderLayerStackingNode::ancestorStackingContextNode() const
 {
-    RenderLayer* ancestor = layer()->parent();
-    while (ancestor && !ancestor->stackingNode()->isStackingContext())
-        ancestor = ancestor->parent();
-    if (ancestor)
-        return ancestor->stackingNode();
-    return 0;
-}
-
-RenderLayerStackingNode* RenderLayerStackingNode::ancestorStackingNode() const
-{
-    RenderLayer* ancestor = layer()->parent();
-    while (ancestor && !ancestor->stackingNode()->isStackingContext())
-        ancestor = ancestor->parent();
-    if (ancestor)
-        return ancestor->stackingNode();
+    for (RenderLayer* ancestor = layer()->parent(); ancestor; ancestor = ancestor->parent()) {
+        RenderLayerStackingNode* stackingNode = ancestor->stackingNode();
+        if (stackingNode->isStackingContext())
+            return stackingNode;
+    }
     return 0;
 }