Add comment explaining extra menu nodes when using Carbon widgets. This comment becomes necessary since I have to sync 324180 to the branch. Follow-up to 324180.

browser/base/content/baseMenuOverlay.xul

@@ -52,7 +52,10 @@
 <script type="application/x-javascript" src="chrome://help/content/contextHelp.js"/>
 
 #ifdef XP_MACOSX
-<!-- nsMenuBarX hides these and uses them to build the Application menu -->
+<!-- nsMenuBarX hides these and uses them to build the Application menu.
+     When using Carbon widgets for Mac OS X widgets, some of these are not
+     used as they only apply to Cocoa widget builds. All version of Firefox
+     through Firefox 2 will use Carbon widgets. -->
     <menupopup id="menu_ToolsPopup">
         <menuitem id="menu_preferences" label="&preferencesCmdMac.label;" key="key_preferencesCmdMac" oncommand="openPreferences();"/>
         <menuitem id="menu_mac_services" label="&servicesMenuMac.label;"/>