console: rename argument of time and timeEnd

Name it timerName instead of label. It is clearer that way and matches
the description in the doc. It is also how it's named in MDN.

PR-URL: nodejs#3166
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

doc/api/console.markdown

@@ -72,18 +72,18 @@ object. This is useful for inspecting large complicated objects. Defaults to
 - `colors` - if `true`, then the output will be styled with ANSI color codes.
 Defaults to `false`. Colors are customizable, see below.
 
-### console.time(label)
+### console.time(timerName)
 
 Starts a timer that can be used to compute the duration of an operation. Timers
 are identified by a unique name. Use the same name when you call
-[`console.timeEnd()`](#console_console_timeend_label) to stop the timer and
+[`console.timeEnd()`](#console_console_timeend_timername) to stop the timer and
 output the elapsed time in milliseconds. Timer durations are accurate to the
 sub-millisecond.
 
-### console.timeEnd(label)
+### console.timeEnd(timerName)
 
 Stops a timer that was previously started by calling
-[`console.time()`](#console_console_time_label) and prints the result to the
+[`console.time()`](#console_console_time_timername) and prints the result to the
 console.
 
 Example:

lib/console.js

@@ -55,19 +55,19 @@ Console.prototype.dir = function(object, options) {
 };
 
 
-Console.prototype.time = function(label) {
-  this._times.set(label, process.hrtime());
+Console.prototype.time = function(timerName) {
+  this._times.set(timerName, process.hrtime());
 };
 
 
-Console.prototype.timeEnd = function(label) {
-  var time = this._times.get(label);
+Console.prototype.timeEnd = function(timerName) {
+  var time = this._times.get(timerName);
   if (!time) {
-    throw new Error('No such label: ' + label);
+    throw new Error('No such timer name: ' + timerName);
   }
   const duration = process.hrtime(time);
   const ms = duration[0] * 1000 + duration[1] / 1e6;
-  this.log('%s: %sms', label, ms.toFixed(3));
+  this.log('%s: %sms', timerName, ms.toFixed(3));
 };