ChromeVox focus not properly shown when navigating: keyboard page

If you navigate to "Change language and input settings"
page and then back to "Keyboard" page, the arrow pointing back
to "Change language and input settings" is not highlighted
when in ChromeVox mode

Steps (in ChromeVox mode):
1. Device
2. Keyboard
3. Change language and input settings
4. Back button

Bug: 1029954
Test: Manual
Change-Id: Ib6c15179f2d217d84365927e2371a83961286f64
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2487866
Commit-Queue: Michael Irani <michaelirani@chromium.org>
Auto-Submit: Michael Irani <michaelirani@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819738}

chrome/browser/resources/settings/chromeos/device_page/device_page.html

@@ -64,7 +64,8 @@
         <settings-subpage
             associated-control="[[$$('#keyboardRow')]]"
             page-title="$i18n{keyboardTitle}">
-          <settings-keyboard prefs="{{prefs}}"></settings-keyboard>
+          <settings-keyboard prefs="{{prefs}}" focus-config="[[focusConfig_]]">
+          </settings-keyboard>
         </settings-subpage>
       </template>
       <template is="dom-if" route-path="/stylus" no-search="[[!hasStylus_]]">

chrome/browser/resources/settings/chromeos/device_page/keyboard.html

@@ -142,17 +142,19 @@
         label="$i18n{showKeyboardShortcutViewer}" external
         deep-link-focus-id$="[[Setting.kKeyboardShortcuts]]"></cr-link-row>
     <template is="dom-if" if="[[!languageSettingsV2Enabled_]]">
-      <cr-link-row class="hr" on-click="onShowLanguageInputTap_"
+      <cr-link-row id="showLanguagesDetails"
+          class="hr" on-click="onShowLanguageInputTap_"
           label="$i18n{keyboardShowLanguageAndInput}"
           role-description="$i18n{subpageArrowRoleDescription}">
       </cr-link-row>
     </template>
     <template is="dom-if" if="[[languageSettingsV2Enabled_]]">
-      <cr-link-row class="hr" on-click="onShowInputSettingsTap_"
+      <cr-link-row id="showLanguagesInput"
+          class="hr" on-click="onShowInputSettingsTap_"
           label="$i18n{keyboardShowInputSettings}"
           role-description="$i18n{subpageArrowRoleDescription}">
       </cr-link-row>
-    </template>     
+    </template>
   </template>
   <script src="keyboard.js"></script>
 </dom-module>

chrome/browser/resources/settings/chromeos/device_page/keyboard.js

@@ -35,6 +35,12 @@ cr.define('settings', function() {
         notify: true,
       },
 
+      /** @private {!Map<string, (string|Function)>} */
+      focusConfig: {
+        type: Object,
+        observer: 'onFocusConfigChange_',
+      },
+
       /** @private Whether to show Caps Lock options. */
       showCapsLock_: Boolean,
 
@@ -174,6 +180,24 @@ cr.define('settings', function() {
       ];
     },
 
+    /** @private */
+    onFocusConfigChange_() {
+      let path, id;
+      if (this.languageSettingsV2Enabled_) {
+        path = settings.routes.OS_LANGUAGES_INPUT.path;
+        id = '#showLanguagesInput';
+      } else {
+        path = settings.routes.OS_LANGUAGES_DETAILS.path;
+        id = '#showLanguageDetails';
+      }
+
+      this.focusConfig.set(path, () => {
+        Polymer.RenderStatus.afterNextRender(this, () => {
+          cr.ui.focusWithoutInk(assert(this.$$(id)));
+        });
+      });
+    },
+
     /**
      * Handler for updating which keys to show.
      * @param {Object} keyboardParams