Simplify resolving filePath in perf/perf.js. [ci skip]

perf/perf.js

@@ -44,7 +44,7 @@
 
     if (!amd) {
       try {
-        return require('fs').realpathSync(result);
+        return require.resolve(result);
       } catch(e) { }
     }
     return result;
@@ -71,10 +71,6 @@
     _._ || _
   ));
 
-  try {
-    filePath = require.resolve(filePath);
-  } catch(e) { }
-
   /** Used to access the Firebug Lite panel (set by `run`) */
   var fbPanel;