1 files changed, 36 insertions, 11 deletions

diff --git a/dom/base/nsIContentInlines.h b/dom/base/nsIContentInlines.h
index 368a0422b..6a9bd7afa 100644
--- a/dom/base/nsIContentInlines.h
+++ b/dom/base/nsIContentInlines.h
@@ -33,14 +33,15 @@ inline mozilla::dom::ShadowRoot* nsIContent::GetShadowRoot() const
   return AsElement()->FastGetShadowRoot();
 }
 
-inline nsINode* nsINode::GetFlattenedTreeParentNode() const
+template<nsIContent::FlattenedParentType Type>
+static inline nsINode*
+GetFlattenedTreeParentNode(const nsINode* aNode)
 {
-  nsINode* parent = GetParentNode();
-
+  nsINode* parent = aNode->GetParentNode();
   // Try to short-circuit past the complicated and not-exactly-fast logic for
   // computing the flattened parent.
   //
-  // There are three cases where we need might something other than parentNode:
+  // There are four cases where we need might something other than parentNode:
   //   (1) The node is an explicit child of an XBL-bound element, re-bound
   //       to an XBL insertion point.
   //   (2) The node is a top-level element in a shadow tree, whose flattened
@@ -48,18 +49,31 @@ inline nsINode* nsINode::GetFlattenedTreeParentNode() const
   //       is the shadow root).
   //   (3) The node is an explicit child of an element with a shadow root,
   //       re-bound to an insertion point.
-  bool needSlowCall = HasFlag(NODE_MAY_BE_IN_BINDING_MNGR) ||
-                      IsInShadowTree() ||
-                      (parent && parent->IsContent() &&
-                       parent->AsContent()->GetShadowRoot());
+  //   (4) We want the flattened parent for style, and the node is the root
+  //       of a native anonymous content subtree parented to the document's
+  //       root element.
+  bool needSlowCall = aNode->HasFlag(NODE_MAY_BE_IN_BINDING_MNGR) ||
+                      aNode->IsInShadowTree() ||
+                      (parent &&
+                       parent->IsContent() &&
+                       parent->AsContent()->GetShadowRoot()) ||
+                      (Type == nsIContent::eForStyle &&
+                       aNode->IsContent() &&
+                       aNode->AsContent()->IsRootOfNativeAnonymousSubtree() &&
+                       aNode->OwnerDoc()->GetRootElement() == parent);
   if (MOZ_UNLIKELY(needSlowCall)) {
-    MOZ_ASSERT(IsContent());
-    return AsContent()->GetFlattenedTreeParentNodeInternal();
+    MOZ_ASSERT(aNode->IsContent());
+    return aNode->AsContent()->GetFlattenedTreeParentNodeInternal(Type);
   }
-
   return parent;
 }
 
+inline nsINode*
+nsINode::GetFlattenedTreeParentNode() const
+{
+  return ::GetFlattenedTreeParentNode<nsIContent::eNotForStyle>(this);
+}
+
 inline nsIContent*
 nsIContent::GetFlattenedTreeParent() const
 {
@@ -67,5 +81,16 @@ nsIContent::GetFlattenedTreeParent() const
   return (parent && parent->IsContent()) ? parent->AsContent() : nullptr;
 }
 
+inline nsINode*
+nsINode::GetFlattenedTreeParentNodeForStyle() const
+{
+  return ::GetFlattenedTreeParentNode<nsIContent::eForStyle>(this);
+}
+
+inline bool
+nsINode::NodeOrAncestorHasDirAuto() const
+{
+  return AncestorHasDirAuto() || (IsElement() && AsElement()->HasDirAuto());
+}
 
 #endif // nsIContentInlines_h