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 af5ba4740e8d765ca8a3a1db31cc51feafec20c5..5873377c18d6eb21e306dac6c55745f772923433 100644
--- a/ppapi/api/private/ppb_nacl_private.idl
+++ b/ppapi/api/private/ppb_nacl_private.idl
@@ -266,4 +266,9 @@ interface PPB_NaCl_Private {
 
   /* Performs internal cleanup when an instance is destroyed. */
   void InstanceDestroyed([in] PP_Instance instance);
+
+  /* Return true if the NaCl debug stub is enabled and the loaded app
+   * will be attached to a debugger.
+   */
+  PP_Bool NaClDebugStubEnabled();
 };