Refactor the process of choosing validators.

src/trusted/service_runtime/sel_main.c

Index: src/trusted/service_runtime/sel_main.c
diff --git a/src/trusted/service_runtime/sel_main.c b/src/trusted/service_runtime/sel_main.c
index 1e320e7331fd59c579705529c98f071e7d1f54af..d664f3aa01ecddd56579e6ad382660b8f6781a91 100644
--- a/src/trusted/service_runtime/sel_main.c
+++ b/src/trusted/service_runtime/sel_main.c
@@ -507,12 +507,6 @@ int main(int  argc,
     }
   }
 
-  nap->enable_dfa_validator = 0;
-  if (getenv("NACL_DANGEROUS_USE_DFA_VALIDATOR") != NULL) {
-    fprintf(stderr, "DANGER! USING THE UNSTABLE DFA VALIDATOR!\n");
-    nap->enable_dfa_validator = 1;
-  }
-
   /* Sanity check. */
   NaClSignalAssertNoHandlers();