Added uma for pin unlock set up.

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

Index: chrome/browser/resources/settings/people_page/lock_screen.js
diff --git a/chrome/browser/resources/settings/people_page/lock_screen.js b/chrome/browser/resources/settings/people_page/lock_screen.js
index f296363be34d22c6969668a110d742ddcf0a9617..60cea9238e91897fd20a26e582b21743b96b9a83 100644
--- a/chrome/browser/resources/settings/people_page/lock_screen.js
+++ b/chrome/browser/resources/settings/people_page/lock_screen.js
@@ -121,5 +121,8 @@ Polymer({
   /** @private */
   onConfigurePin_: function() {
     this.$.setupPin.open();
+    chrome.send('metricsHandler:recordInHistogram',
+        [PinUnlockUmaHistogramName, PinUnlockSetupType.CHOOSE_PIN_OR_PASSWORD,
+         PinUnlockSetupType.STAGE_MAX_BUCKET]);
   },
 });