Check NaCl debug mask (not just flag) before choosing PNaCl debug URL.

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 3249b999ae04d8005be187c043a58c683b944137..3e8bbfd914716c74aa96c075a8dfaadb564e1150 100644
--- a/ppapi/api/private/ppb_nacl_private.idl
+++ b/ppapi/api/private/ppb_nacl_private.idl
@@ -284,10 +284,10 @@ 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.
+  /* Return true if the NaCl debug stub is enabled and the app loaded from
+   * alleged_nmf_url will be attached to a debugger.
    */
-  PP_Bool NaClDebugStubEnabled();
+  PP_Bool NaClDebugEnabledForURL([in] str_t alleged_nmf_url);
 
   /* Returns the kind of SFI sandbox implemented by NaCl on this
   /* platform.