Fix a11y on navigation/directory tree

This CL fixes the keyboard navigation when using screen reader/
Chromevox.

The main fix is to force focus on the cr.ui.Tree/DirectoryTree element
when navigating with Chromevox keyboard shortcut "Search+right arrow",
before the focus was staying on "body" element so Tree couldn't handle
the keyboard events to expand/collapse directories.

It's a series of small fixes.

1. Fix text read by Chromevox when navigating on directories, it was
reading all sub-directories names, instead of only the current focused
directory's name, fixed by adding |id| to each entries' label element,
to make existing |aria-labelledby| attribute work for screen reader.
This was broken because we overwrite the |innerHTML| from
|cr.ui.TreeItem|, losing the |id|.

2. Listen to |click| event on DirectoryTree and forces the focus to it
when the focus/activeElement is the "body" element. This happens when
Chromevox issues the |click| event when user press "Search+right arrow".

3. Replace |cr.ui.Tree|'s |role| attribute from "group" to "navigation",
which is a "landmark" type which is recommended [1]. This required to
change |cr.ui.Tree| to not overwrite existing |role| attribute.


[1] - https://developers.google.com/web/fundamentals/accessibility/how-to-review#take_advantage_of_headings_and_landmarks

Bug: 755278
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: If33be610e1d28f0a69205ee148783328a367fe80
Reviewed-on: https://chromium-review.googlesource.com/985772
Commit-Queue: Luciano Pacheco (SYD) <lucmult@chromium.org>
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Sasha Morrissey <sashab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553917}

ui/file_manager/file_manager/foreground/js/ui/directory_tree.js

@@ -106,12 +106,16 @@ var MENU_TREE_ITEM_INNER_HTML =
  */
 function DirectoryItem(label, tree) {
   var item = /** @type {DirectoryItem} */ (new cr.ui.TreeItem());
+  // Get the original label id defined by TreeItem, before overwriting
+  // prototype.
+  var labelId = item.labelElement.id;
   item.__proto__ = DirectoryItem.prototype;
   item.parentTree_ = tree;
   item.directoryModel_ = tree.directoryModel;
   item.fileFilter_ = tree.directoryModel.getFileFilter();
 
   item.innerHTML = TREE_ITEM_INNER_HTML;
+  item.labelElement.id = labelId;
   item.addEventListener('expand', item.onExpand_.bind(item), false);
 
   // Listen for collapse because for the delayed expansion case all
@@ -858,6 +862,9 @@ DriveVolumeItem.prototype.selectByEntry = function(entry) {
  */
 function ShortcutItem(modelItem, tree) {
   var item = /** @type {ShortcutItem} */ (new cr.ui.TreeItem());
+  // Get the original label id defined by TreeItem, before overwriting
+  // prototype.
+  var labelId = item.labelElement.id;
   item.__proto__ = ShortcutItem.prototype;
 
   item.parentTree_ = tree;
@@ -865,6 +872,7 @@ function ShortcutItem(modelItem, tree) {
   item.modelItem_ = modelItem;
 
   item.innerHTML = TREE_ITEM_INNER_HTML;
+  item.labelElement.id = labelId;
 
   var icon = item.querySelector('.icon');
   icon.classList.add('item-icon');
@@ -979,11 +987,15 @@ ShortcutItem.prototype.activate = function() {
  */
 function MenuItem(modelItem, tree) {
   var item = new cr.ui.TreeItem();
+  // Get the original label id defined by TreeItem, before overwriting
+  // prototype.
+  var labelId = item.labelElement.id;
   item.__proto__ = MenuItem.prototype;
 
   item.parentTree_ = tree;
   item.modelItem_ = modelItem;
   item.innerHTML = MENU_TREE_ITEM_INNER_HTML;
+  item.labelElement.id = labelId;
   item.label = modelItem.label;
 
   item.menuButton_ = /** @type {!cr.ui.MenuButton} */(queryRequiredElement(
@@ -1054,12 +1066,16 @@ MenuItem.prototype.activate = function() {
  */
 function RecentItem(modelItem, tree) {
   var item = new cr.ui.TreeItem();
+  // Get the original label id defined by TreeItem, before overwriting
+  // prototype.
+  var labelId = item.labelElement.id;
   item.__proto__ = RecentItem.prototype;
 
   item.parentTree_ = tree;
   item.modelItem_ = modelItem;
   item.dirEntry_ = modelItem.entry;
   item.innerHTML = TREE_ITEM_INNER_HTML;
+  item.labelElement.id = labelId;
   item.label = modelItem.label;
 
   var icon = queryRequiredElement('.icon', item);
@@ -1370,6 +1386,15 @@ DirectoryTree.prototype.decorateDirectoryTree = function(
       'entries-changed',
       this.onEntriesChanged_.bind(this));
 
+  this.addEventListener('click', (event) => {
+    // Chromevox triggers |click| without switching focus, we force the focus
+    // here so we can handle further keyboard/mouse events to expand/collapse
+    // directories.
+    if (document.activeElement === document.body) {
+      this.focus();
+    }
+  });
+
   this.privateOnDirectoryChangedBound_ =
       this.onDirectoryContentChanged_.bind(this);
   chrome.fileManagerPrivate.onDirectoryChanged.addListener(

ui/file_manager/file_manager/main.html

@@ -421,7 +421,7 @@
     <div class="dialog-container">
       <div class="dialog-navigation-list">
         <div class="dialog-navigation-list-contents">
-          <tree id="directory-tree" tabindex="21"></tree>
+          <tree id="directory-tree" role="navigation" tabindex="21"></tree>
         </div>
         <div class="dialog-navigation-list-footer">
           <div id="progress-center" hidden>

ui/file_manager/file_manager/test/create_new_folder.js

@@ -39,14 +39,12 @@ test.selectFirstListItem = function() {
  */
 test.createNewFolder = function(initialEntrySet) {
   var maxListItemId = test.maxListItemId();
-  return Promise.resolve()
-      .then(() => {
-        // Push Ctrl + E.
-        assertTrue(
-            test.fakeKeyDown('#file-list', 'e', 'U+0045', true, false, false));
-        // Wait for rename text field.
-        return test.waitForElement('li[renaming] input.rename');
-      })
+  // Force focus to file list.
+  document.querySelector('#file-list:not([hidden])').focus();
+  // Press Ctrl+E to create a new folder.
+  assertTrue(test.fakeKeyDown('#file-list', 'e', 'U+0045', true, false, false));
+  // Wait for rename text field.
+  return test.waitForElement('li[renaming] input.rename')
       .then(() => {
         var elements =
             document.querySelectorAll('div.detail-table > list > li[selected]');

ui/file_manager/integration_tests/file_manager/transfer.js

@@ -40,6 +40,11 @@ function copyBetweenVolumes(targetFile,
       chrome.test.assertTrue(result);
       remoteCall.waitForFiles(appId, srcContents).then(this.next);
     },
+    // Set focus on the file list.
+    function() {
+      remoteCall.callRemoteTestUtil(
+          'focus', appId, ['#file-list:not([hidden])'], this.next);
+    },
     // Select the source file.
     function() {
       remoteCall.callRemoteTestUtil(

ui/webui/resources/js/cr/ui/tree.js

@@ -58,7 +58,8 @@ cr.define('cr.ui', function() {
       this.addEventListener('dblclick', this.handleDblClick);
       this.addEventListener('keydown', this.handleKeyDown);
 
-      this.setAttribute('role', 'group');
+      if (!this.hasAttribute('role'))
+        this.setAttribute('role', 'group');
     },
 
     /**