Including nsString.h directly. It is included indirectly by nsFileSpec. This

prep work for the nsIFile landing.

rdf/tests/rdfpoll/rdfpoll.cpp

@@ -55,6 +55,7 @@
 #include "plevent.h"
 #include "plstr.h"
 #include "nsParserCIID.h"
+#include "nsString.h"
 
 #if defined(XP_PC)
 #define DOM_DLL    "jsdom.dll"