Make tests/units/* compile without warnings in non-test mode

(if not usefully)

tests/unit/profile/lib.rs

@@ -2,10 +2,11 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#![cfg(test)]
+
 extern crate ipc_channel;
 extern crate profile;
 extern crate profile_traits;
 extern crate servo_allocator;
 
-#[cfg(test)]
 mod time;