Make the simple cases of dynamic changes of -moz-box-ordinal-group work correctly. (Bug 555987) r=dbaron

layout/reftests/box-ordinal/reftest.list

@@ -1,6 +1,6 @@
 == dynamic-1-remove-to-none-grouped.xul dynamic-1-ref.xul
-fails == dynamic-1-add-to-one-grouped.xul dynamic-1-ref.xul
+== dynamic-1-add-to-one-grouped.xul dynamic-1-ref.xul
 == dynamic-1-remove-to-one-grouped-1.xul dynamic-1-ref.xul
 fails == dynamic-1-remove-to-one-grouped-2.xul dynamic-1-ref.xul
 == dynamic-1-add-to-two-grouped-1.xul dynamic-1-ref.xul
-fails == dynamic-1-add-to-two-grouped-2.xul dynamic-1-ref.xul
+== dynamic-1-add-to-two-grouped-2.xul dynamic-1-ref.xul

layout/xul/base/src/nsBoxFrame.cpp

@@ -1054,6 +1054,12 @@ nsBoxFrame::InsertFrames(nsIAtom*        aListName,
    if (mLayoutManager)
      mLayoutManager->ChildrenInserted(this, state, aPrevFrame, newFrames);
 
+   // Make sure to check box order _after_ notifying the layout
+   // manager; otherwise the slice we give the layout manager will
+   // just be bogus.  If the layout manager cares about the order, we
+   // just lose.
+   CheckBoxOrder(state);
+
 #ifdef DEBUG_LAYOUT
    // if we are in debug make sure our children are in debug as well.
    if (mState & NS_STATE_CURRENTLY_IN_DEBUG)
@@ -1081,6 +1087,12 @@ nsBoxFrame::AppendFrames(nsIAtom*        aListName,
    if (mLayoutManager)
      mLayoutManager->ChildrenAppended(this, state, newFrames);
 
+   // Make sure to check box order _after_ notifying the layout
+   // manager; otherwise the slice we give the layout manager will
+   // just be bogus.  If the layout manager cares about the order, we
+   // just lose.
+   CheckBoxOrder(state);
+
 #ifdef DEBUG_LAYOUT
    // if we are in debug make sure our children are in debug as well.
    if (mState & NS_STATE_CURRENTLY_IN_DEBUG)