timers: optimize callback call: bind -> arrow

ES6 arrow functions are much more efficient than `.bind()` functions.

PR-URL: https://github.com/nodejs/node/pull/4038
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

lib/timers.js

@@ -193,21 +193,21 @@ exports.setTimeout = function(callback, after) {
     case 2:
       break;
     case 3:
-      ontimeout = callback.bind(timer, arguments[2]);
+      ontimeout = () => callback.call(timer, arguments[2]);
       break;
     case 4:
-      ontimeout = callback.bind(timer, arguments[2], arguments[3]);
+      ontimeout = () => callback.call(timer, arguments[2], arguments[3]);
       break;
     case 5:
       ontimeout =
-          callback.bind(timer, arguments[2], arguments[3], arguments[4]);
+        () => callback.call(timer, arguments[2], arguments[3], arguments[4]);
       break;
     // slow case
     default:
       var args = new Array(length - 2);
       for (var i = 2; i < length; i++)
         args[i - 2] = arguments[i];
-      ontimeout = callback.apply.bind(callback, timer, args);
+      ontimeout = () => callback.apply(timer, args);
       break;
   }
   timer._onTimeout = ontimeout;
@@ -248,20 +248,20 @@ exports.setInterval = function(callback, repeat) {
     case 2:
       break;
     case 3:
-      ontimeout = callback.bind(timer, arguments[2]);
+      ontimeout = () => callback.call(timer, arguments[2]);
       break;
     case 4:
-      ontimeout = callback.bind(timer, arguments[2], arguments[3]);
+      ontimeout = () => callback.call(timer, arguments[2], arguments[3]);
       break;
     case 5:
       ontimeout =
-          callback.bind(timer, arguments[2], arguments[3], arguments[4]);
+        () => callback.call(timer, arguments[2], arguments[3], arguments[4]);
       break;
     default:
       var args = new Array(length - 2);
       for (var i = 2; i < length; i += 1)
         args[i - 2] = arguments[i];
-      ontimeout = callback.apply.bind(callback, timer, args);
+      ontimeout = () => callback.apply(timer, args);
       break;
   }
   timer._onTimeout = wrapper;
@@ -273,7 +273,7 @@ exports.setInterval = function(callback, repeat) {
   return timer;
 
   function wrapper() {
-    timer._repeat.call(this);
+    timer._repeat();
 
     // Timer might be closed - no point in restarting it
     if (!timer._repeat)