process: improve performance of nextTick

This replaces TickObject with an object literal. This offers
performance improvements of up to ~20%.

PR-URL: nodejs#8932
Reviewed-By: Claudio Rodriguez <cjrodr@yahoo.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

lib/internal/process/next_tick.js

@@ -131,12 +131,6 @@ function setupNextTick() {
     } while (tickInfo[kLength] !== 0);
   }
 
-  function TickObject(c, args) {
-    this.callback = c;
-    this.domain = process.domain || null;
-    this.args = args;
-  }
-
   function nextTick(callback) {
     if (typeof callback !== 'function')
       throw new TypeError('callback is not a function');
@@ -151,7 +145,11 @@ function setupNextTick() {
         args[i - 1] = arguments[i];
     }
 
-    nextTickQueue.push(new TickObject(callback, args));
+    nextTickQueue.push({
+      callback,
+      domain: process.domain || null,
+      args
+    });
     tickInfo[kLength]++;
   }
 }