OsSettingsLanguages: Add sub-labels for Languages and Inputs rows

Googlers: a screenshot of the new sub-labels can be found here:
http://screen/345FdDordriQRcu

Fixed: 1146366
Test: Manual test
Change-Id: I49ca8a731b7ef1d63d794368ff27b355298e382d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2525463Reviewed-by: My Nguyen <myy@chromium.org>
Commit-Queue: Michael Cui <mlcui@google.com>
Cr-Commit-Position: refs/heads/master@{#828008}

chrome/browser/resources/settings/chromeos/os_languages_page/os_languages_section.html

@@ -35,8 +35,7 @@
               id="languagesSubpageTrigger"
               label="$i18n{osLanguagesPageTitle}"
               sub-label="[[getSubLabel_(languages.prospectiveUILanguage,
-                  languages.inputMethods.currentId,
-                  languages.inputMethods.enabled, languageHelper)]]"
+                  languages.inputMethods.currentId, languageHelper)]]"
               on-click="onLanguagesTap_"
               role-description="$i18n{subpageArrowRoleDescription}">
           </cr-link-row>
@@ -45,6 +44,8 @@
             <cr-link-row
                 id="languagesPageTrigger"
                 label="$i18n{languagesPageTitle}"
+                sub-label="[[getLanguageDisplayName_(
+                    languages.prospectiveUILanguage, languageHelper)]]"
                 on-click="onLanguagesV2Click_"
                 role-description="$i18n{subpageArrowRoleDescription}">
             </cr-link-row>
@@ -52,6 +53,8 @@
                 class="hr"
                 id="inputPageTrigger"
                 label="$i18n{inputPageTitle}"
+                sub-label="[[getInputMethodDisplayName_(
+                  languages.inputMethods.currentId, languageHelper)]]"
                 on-click="onInputClick_"
                 role-description="$i18n{subpageArrowRoleDescription}">
             </cr-link-row>

chrome/browser/resources/settings/chromeos/os_languages_page/os_languages_section.js

@@ -94,22 +94,18 @@ Polymer({
    * @param {string|undefined} uiLanguage Current UI language fully specified,
    *     e.g. "English (United States)".
    * @param {string} id The input method ID, e.g. "US Keyboard".
-   * @param {!Array<!chrome.languageSettingsPrivate.InputMethod>}
-   *     enabledInputMethods The list of currently enabled input methods.
    * @param {!LanguageHelper} languageHelper The LanguageHelper object.
    * @return {string} A sublabel for the 'Languages and input' row
    * @private
    */
-  getSubLabel_(uiLanguage, id, enabledInputMethods, languageHelper) {
-    if (uiLanguage === undefined) {
+  getSubLabel_(uiLanguage, id, languageHelper) {
+    const languageDisplayName =
+        this.getLanguageDisplayName_(uiLanguage, languageHelper);
+    if (!languageDisplayName) {
       return '';
     }
-    const languageDisplayName =
-        languageHelper.getLanguage(uiLanguage).displayName;
-    const inputMethod = enabledInputMethods.find(function(inputMethod) {
-      return inputMethod.id === id;
-    });
-    const inputMethodDisplayName = inputMethod ? inputMethod.displayName : '';
+    const inputMethodDisplayName =
+        this.getInputMethodDisplayName_(id, languageHelper);
     if (!inputMethodDisplayName) {
       return languageDisplayName;
     }
@@ -117,4 +113,37 @@ Polymer({
     // element list (i.e. it's a standard format).
     return languageDisplayName + ', ' + inputMethodDisplayName;
   },
+
+  /**
+   * @param {string|undefined} code The language code of the language.
+   * @param {!LanguageHelper} languageHelper The LanguageHelper object.
+   * @return {string} The display name of the language specified.
+   * @private
+   */
+  getLanguageDisplayName_(code, languageHelper) {
+    if (!code) {
+      return '';
+    }
+    const language = languageHelper.getLanguage(code);
+    if (!language) {
+      return '';
+    }
+    return language.displayName;
+  },
+
+  /**
+   * @param {string} id The input method ID.
+   * @param {!LanguageHelper} languageHelper The LanguageHelper object.
+   * @return {string} The display name of the input method.
+   * @private
+   */
+  getInputMethodDisplayName_(id, languageHelper) {
+    // LanguageHelper.getInputMethodDisplayName will throw an error if the ID
+    // isn't found, such as when using CrOS on Linux.
+    try {
+      return languageHelper.getInputMethodDisplayName(id);
+    } catch (_) {
+      return '';
+    }
+  },
 });