Added uma for pin unlock set up.

chrome/browser/resources/settings/people_page/password_prompt_dialog.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-password-prompt-dialog' shows a dialog which asks for the user to
  * enter their password. It validates the password is correct. Once the user has
  * entered their account password, the page fires an 'authenticated' event and
@@ skipping 139 matching lines @@
           // Reset the password so that any cached references to this.setModes
           // will fail.
           password = '';
           this.setModes = null;
         }
 
         this.clearAccountPasswordTimeout_ = setTimeout(
           clearSetModes.bind(this), PASSWORD_ACTIVE_DURATION_MS);
         // Closing the dialog will clear this.password_.
         this.$.dialog.close();
+        chrome.send('metricsHandler:recordInHistogram',
+            [PinUnlockUmaHistogramName,
+             PinUnlockSetupType.ENTER_PASSWORD_CORRECTLY,
+             PinUnlockSetupType.MAX_BUCKET]);
       }
     }
 
     checkAccountPassword_(this.password_, onPasswordChecked.bind(this));
   },
 
   /** @private */
   onPasswordChanged_: function() {
     this.passwordInvalid_ = false;
   },
 
   /** @private */
   enableConfirm_: function() {
     return !!this.password_ && !this.passwordInvalid_;
   }
 });
 
 })();