bugzilla bug 84532 r=shliang sr=hewitt line break between subject and body of message.

themes/classic/messenger/mac/messageHeader.css

@@ -33,8 +33,15 @@ Rights Reserved.
 #expandedHeaderView
   {
     min-width             : 1px;
+    border-bottom: 1px solid #999999;
   }
 
+#collapsedHeaderView[collapsed="true"],
+#expandedHeaderView[collapsed="true"]{
+	border-bottom: none;
+
+}
+
 mail-emailaddress {
   -moz-binding: url(chrome://messenger/content/mailWidgets.xml#mail-emailaddress);
   display: -moz-inline-box;