Fix bug 86671 by initializing mDNSWindow member variable for XP_WIN.

r=neeti, sr=darin, a=asa.

netwerk/dns/src/nsDnsService.cpp

@@ -873,6 +873,9 @@ nsDNSService::nsDNSService()
     , mState(DNS_NOT_INITIALIZED)
 #if defined(XP_MAC)
     , mServiceRef(nsnull)
+#endif
+#if defined(XP_WIN)
+    , mDNSWindow(nsnull)
 #endif
 #ifdef DNS_TIMING
     , mCount(0)