Have PNaCl use debug pexe URL instead of stripped pexe w/ kEnableNaClDebug

ppapi/api/private/ppb_nacl_private.idl

Index: ppapi/api/private/ppb_nacl_private.idl
diff --git a/ppapi/api/private/ppb_nacl_private.idl b/ppapi/api/private/ppb_nacl_private.idl
index 57e883aa769b8eba928be1e602dcc29af72d232b..703b482dbfc761d7cd3d8c1df80be86cbc182856 100644
--- a/ppapi/api/private/ppb_nacl_private.idl
+++ b/ppapi/api/private/ppb_nacl_private.idl
@@ -264,4 +264,9 @@ interface PPB_NaCl_Private {
   void ReportLoadError([in] PP_Instance instance,
                        [in] PP_NaClError error,
                        [in] PP_Bool is_installed);
+
+  /* Return true if the NaCl debug stub is enabled and the loaded app
+   * will be attached to a debugger.
+   */
+  PP_Bool NaClDebugStubEnabled();
 };