Use performance-now instead of custom solution

package.json

@@ -38,6 +38,7 @@
     "mime-types": "~2.1.7",
     "node-uuid": "~1.4.7",
     "oauth-sign": "~0.8.1",
+    "performance-now": "^0.2.0",
     "qs": "~6.3.0",
     "stringstream": "~0.0.4",
     "tough-cookie": "~2.3.0",

request.js

@@ -28,6 +28,7 @@ var http = require('http')
   , Multipart = require('./lib/multipart').Multipart
   , Redirect = require('./lib/redirect').Redirect
   , Tunnel = require('./lib/tunnel').Tunnel
+  , now = require('performance-now')
 
 var safeStringify = helpers.safeStringify
   , isReadStream = helpers.isReadStream
@@ -36,7 +37,6 @@ var safeStringify = helpers.safeStringify
   , copy = helpers.copy
   , version = helpers.version
   , globalCookieJar = cookies.jar()
-  , hrTimeStart
 
 
 var globalPool = {}
@@ -92,28 +92,6 @@ function responseToJSON() {
   }
 }
 
-function getHrTime() {
-  if (typeof process === 'undefined' || !process.hrtime) {
-    return 0
-  }
-
-  var hr = process.hrtime()
-  // convert to nanoseconds
-  return hr[0] * 1e9 + hr[1]
-}
-
-hrTimeStart = getHrTime()
-
-function getTimeFromStart() {
-  // in the browser, use performance.now()
-  if (typeof performance !== 'undefined' && performance.now) {
-    return performance.now()
-  }
-
-  // in nodejs, use process.hrtime() (converting back to milliseconds)
-  return (getHrTime() - hrTimeStart) / 1e6
-}
-
 function Request (options) {
   // if given the method property in options, set property explicitMethod to true
 
@@ -739,7 +717,7 @@ Request.prototype.start = function () {
   var self = this
 
   if (self.timing) {
-    var startTime = getTimeFromStart()
+    var startTime = now()
   }
 
   if (self._aborted) {
@@ -799,9 +777,9 @@ Request.prototype.start = function () {
   })
   self.req.on('socket', function(socket) {
     if (self.timing) {
-      self.timings.socket = getTimeFromStart()
+      self.timings.socket = now()
       socket.on('connect', function() {
-        self.timings.connect = getTimeFromStart()
+        self.timings.connect = now()
       })
     }
 
@@ -888,13 +866,13 @@ Request.prototype.onRequestResponse = function (response) {
   var self = this
 
   if (self.timing) {
-    self.timings.response = getTimeFromStart()
+    self.timings.response = now()
   }
 
   debug('onRequestResponse', self.uri.href, response.statusCode, response.headers)
   response.on('end', function() {
     if (self.timing) {
-      self.timings.end = getTimeFromStart()
+      self.timings.end = now()
 
       self.timings.dns = self.timings.socket - self.timings.start
       self.timings.tcp = self.timings.connect - self.timings.socket