Added uma for pin unlock set up.

chrome/browser/resources/settings/people_page/lock_screen.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview
  * 'settings-lock-screen' allows the user to change how they unlock their
  * device.
  *
  * Example:
@@ skipping 103 matching lines @@
   /** @private */
   getSetupPinText_: function() {
     if (this.hasPin)
       return this.i18n('lockScreenChangePinButton');
     return this.i18n('lockScreenSetupPinButton');
   },
 
   /** @private */
   onConfigurePin_: function() {
     this.$.setupPin.open();
+    chrome.send('metricsHandler:recordInHistogram',
+        [PinUnlockUmaHistogramName, PinUnlockSetupType.CHOOSE_PIN_OR_PASSWORD,
+         PinUnlockSetupType.STAGE_MAX_BUCKET]);
   },
 });