Bug 334690. Fix regression in z-ordering of table cell content for event handling. r=bernd

layout/tables/nsTableFrame.cpp

@@ -1405,19 +1405,18 @@ nsTableFrame::DisplayGenericTablePart(nsDisplayListBuilder* aBuilder,
                                       PRBool aIsRoot)
 {
   nsDisplayList eventsBorderBackground;
-  // If we need to sort the event backgrounds, then we'll put descendant
-  // border-backgrounds into their own list so we don't accidentally sort
-  // some ancestor's border-background.
+  // If we need to sort the event backgrounds, then we'll put descendants'
+  // display items into their own set of lists.
   PRBool sortEventBackgrounds = aIsRoot && aBuilder->IsForEventDelivery();
-  nsDisplayListSet lists(aLists,
-    sortEventBackgrounds ? &eventsBorderBackground : aLists.BorderBackground());
+  nsDisplayListCollection separatedCollection;
+  const nsDisplayListSet* lists = sortEventBackgrounds ? &separatedCollection : &aLists;
   
   // Create dedicated background display items per-frame when we're
   // handling events.
   // XXX how to handle collapsed borders?
   if (aBuilder->IsForEventDelivery() &&
       aFrame->IsVisibleForPainting(aBuilder)) {
-    nsresult rv = lists.BorderBackground()->AppendNewToTop(new (aBuilder)
+    nsresult rv = lists->BorderBackground()->AppendNewToTop(new (aBuilder)
         nsDisplayBackground(aFrame));
     NS_ENSURE_SUCCESS(rv, rv);
   }
@@ -1432,7 +1431,7 @@ nsTableFrame::DisplayGenericTablePart(nsDisplayListBuilder* aBuilder,
   // lets us get cell borders into the nsTableFrame's BorderBackground list.
   nsIFrame* kid = aFrame->GetFirstChild(nsnull);
   while (kid) {
-    nsresult rv = aFrame->BuildDisplayListForChild(aBuilder, kid, aDirtyRect, lists);
+    nsresult rv = aFrame->BuildDisplayListForChild(aBuilder, kid, aDirtyRect, *lists);
     NS_ENSURE_SUCCESS(rv, rv);
     kid = kid->GetNextSibling();
   }
@@ -1441,11 +1440,11 @@ nsTableFrame::DisplayGenericTablePart(nsDisplayListBuilder* aBuilder,
     // Ensure that the table frame event background goes before the
     // table rowgroups event backgrounds, before the table row event backgrounds,
     // before everything else (cells and their blocks)
-    eventsBorderBackground.Sort(aBuilder, CompareByTablePartRank, nsnull);
-    aLists.BorderBackground()->AppendToTop(&eventsBorderBackground);
+    separatedCollection.BorderBackground()->Sort(CompareByTablePartRank, nsnull);
+    separatedCollection.MoveTo(aLists);
   }
   
-  return aFrame->DisplayOutline(aBuilder, lists);
+  return aFrame->DisplayOutline(aBuilder, aLists);
 }
 
 // table paint code is concerned primarily with borders and bg color