Add bug number to comment.

widget/src/windows/nsNativeThemeWin.cpp

@@ -1548,8 +1548,9 @@ nsNativeThemeWin::GetMinimumWidgetSize(nsIRenderingContext* aContext, nsIFrame*
                  // so use the min-size request value (of 0).
 
   // We should let HTML buttons shrink to their min size.
-  // FIXME: We should probably really separate GetPreferredWidgetSize
-  // from GetMinimumWidgetSize, so callers can use the one they want.
+  // FIXME bug 403934: We should probably really separate
+  // GetPreferredWidgetSize from GetMinimumWidgetSize, so callers can
+  // use the one they want.
   if (aWidgetType == NS_THEME_BUTTON &&
       aFrame->GetContent()->IsNodeOfType(nsINode::eHTML))
     sizeReq = 0; /* TS_MIN */