Bug 1276669 - part 8 - add a comment in NS_InitXPCOM2 to make static atom initialization less cryptic; r=erahm

This comment makes things slightly more greppable.

xpcom/build/XPCOMInit.cpp

@@ -735,7 +735,9 @@ NS_InitXPCOM2(nsIServiceManager** aResult,
   SharedThreadPool::InitStatics();
 
   // Force layout to spin up so that nsContentUtils is available for cx stack
-  // munging.
+  // munging.  Note that layout registers a number of static atoms, and also
+  // seals the static atom table, so NS_RegisterStaticAtom may not be called
+  // beyond this point.
   nsCOMPtr<nsISupports> componentLoader =
     do_GetService("@mozilla.org/moz/jsloader;1");