Add uma logging for user visit language settings.

[email protected]

(cherry picked from commit b350ff3)

Bug: 759410
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ibbd2b67ee368c7cb4fb0daa79aace64fc8c1a95c
Reviewed-on: https://chromium-review.googlesource.com/640273
Reviewed-by: Michael Giuffrida <[email protected]>
Reviewed-by: Jesse Doherty <[email protected]>
Reviewed-by: Dave Schuyler <[email protected]>
Commit-Queue: Renjie Liu <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#499557}
Reviewed-on: https://chromium-review.googlesource.com/654461
Reviewed-by: Marti Wong <[email protected]>
Cr-Commit-Position: refs/branch-heads/3202@{#61}
Cr-Branched-From: fa6a5d8-refs/heads/master@{#499098}

chrome/browser/resources/settings/languages_page/languages_page.js

@@ -14,6 +14,12 @@ cr.exportPath('settings');
  */
 settings.kMenuCloseDelay = 100;
 
+/**
+ * Name of the language setting is shown uma histogram.
+ * @type {string}
+ */
+const LANGUAGE_SETTING_IS_SHOWN_UMA_NAME = 'Translate.LanguageSettingsIsShown';
+
 (function() {
 'use strict';
 
@@ -58,6 +64,15 @@ Polymer({
      */
     detailLanguage_: Object,
 
+    /**
+     * Whether the language settings list is opened.
+     * @private
+     */
+    languagesOpened_: {
+      type: Boolean,
+      observer: 'onLanguagesOpenedChanged_',
+    },
+
     /** @private */
     showAddLanguagesDialog_: Boolean,
 
@@ -523,6 +538,19 @@ Polymer({
     menu.showAt(/** @type {!Element} */ (e.target));
   },
 
+  /**
+   * @param {boolean} newVal The new value of languagesOpened_.
+   * @param {boolean} oldVal The old value of languagesOpened_.
+   * @private
+   */
+  onLanguagesOpenedChanged_: function(newVal, oldVal) {
+    if (!oldVal && newVal) {
+      chrome.send(
+          'metricsHandler:recordBooleanHistogram',
+          [LANGUAGE_SETTING_IS_SHOWN_UMA_NAME, true]);
+    }
+  },
+
   /**
    * Closes the shared action menu after a short delay, so when a checkbox is
    * tapped it can be seen to change state before disappearing.

tools/metrics/histograms/histograms.xml

@@ -84039,6 +84039,18 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Translate.LanguageSettingsIsShown" enum="BooleanShown">
+  <owner>[email protected]</owner>
+  <summary>
+    Log everytime the language settings page is shown. This can be either user
+    visits chrome://settings/languages or user visits the advanced languages
+    card in chrome://settings. With this stat, we will be able to understand how
+    well the language model is doing by looking into how the number changes over
+    time. In additiona to that, we are also interested in how many users ever
+    visit the languages settings card.
+  </summary>
+</histogram>
+
 <histogram name="Translate.LanguageVerification"
     enum="TranslateLanguageVerification">
   <owner>[email protected]</owner>