Change the FrameNeedsReflow API to pass the dirty flags to be added directly tothe method, instead of setting them before calling the method. That way we canavoid reflowing the ancestor of a reflow root which is not itself dirty but hasdirty children. This also makes it harder to set dirty bits inconsistentlywith the FrameNeedsReflow call. Bug 378784, r+sr=dbaron, pending rbs' reviewon the mathml parts.

layout/forms/nsHTMLButtonControlFrame.cpp

@@ -293,8 +293,7 @@ nsHTMLButtonControlFrame::Reflow(nsPresContext* aPresContext,
 
   // XXXbz Eventually we may want to check-and-bail if
   // !aReflowState.ShouldReflowAllKids() &&
-  // !(firstKid->GetStateBits() &
-  //   (NS_FRAME_IS_DIRTY | NS_FRAME_HAS_DIRTY_CHILDREN)).
+  // !NS_SUBTREE_DIRTY(firstKid).
   // We'd need to cache our ascent for that, of course.
   
   nsMargin focusPadding = mRenderer.GetAddedButtonBorderAndPadding();