diff --git a/mozilla/layout/forms/nsFileControlFrame.cpp b/mozilla/layout/forms/nsFileControlFrame.cpp
index 3bb454bab58..d658a88315c 100644
--- a/mozilla/layout/forms/nsFileControlFrame.cpp
+++ b/mozilla/layout/forms/nsFileControlFrame.cpp
@@ -603,6 +603,10 @@ nsFileControlFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                                      const nsRect&           aDirtyRect,
                                      const nsDisplayListSet& aLists)
 {
+  // Our background is inherited to the text input, and we don't really want to
+  // paint it or out padding and borders (which we never have anyway, per
+  // styles in forms.css) -- doing it just makes us look ugly in some cases and
+  // has no effect in others.
   nsDisplayListCollection tempList;
   nsresult rv = nsAreaFrame::BuildDisplayList(aBuilder, aDirtyRect, tempList);
   if (NS_FAILED(rv))