Added uma for pin unlock set up.

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

Index: chrome/browser/resources/settings/people_page/lock_screen_constants.js
diff --git a/chrome/browser/resources/settings/people_page/lock_screen_constants.js b/chrome/browser/resources/settings/people_page/lock_screen_constants.js
new file mode 100644
index 0000000000000000000000000000000000000000..33d03c8012377573f25d619383867171f75e7a9e
--- /dev/null
+++ b/chrome/browser/resources/settings/people_page/lock_screen_constants.js
@@ -0,0 +1,43 @@
+// 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 Constants used for logging the pin unlock setup uma.
+ */
+
+/**
+ * Name of the pin unlock setup uma histogram.
+ * @type {string}
+ */
+var PinUnlockUmaHistogramName = 'Settings.PinUnlockSetup';
+
+/**
+ * Stages the user can enter while setting up pin unlock.
+ * @enum {number}
+ */
+var LockScreenProgress = {
+  START_SCREEN_LOCK: 0,
+  ENTER_PASSWORD_CORRECTLY: 1,
+  CHOOSE_PIN_OR_PASSWORD: 2,
+  ENTER_PIN: 3,
+  CONFIRM_PIN: 4,
+  MAX_BUCKET: 5
+};
+
+/**
+ * Helper function to send the progress of the pin setup to be recorded in the
+ * histogram.
+ * @param {LockScreenProgress} currentProgress
+ */
+var recordLockScreenProgress = function(currentProgress) {

[Dan Beam, 2016/12/16 08:31:01]

maybe put this in a namespace?  i.e. settings.recordLockScreenProgress?

[sammiequon, 2016/12/17 18:17:13]

Done.

+  if (currentProgress >= LockScreenProgress.MAX_BUCKET) {
+    console.error('Expected a enumeration value of ' +
+        LockScreenProgress.MAX_BUCKET + ' or lower: Received ' +
+        currentProgress + '.');
+    return;
+  }
+  chrome.send('metricsHandler:recordInHistogram',
+      [PinUnlockUmaHistogramName, currentProgress,
+       LockScreenProgress.MAX_BUCKET]);
+};