[Switch Access] Clarify singleton object

The Switch Access object has always had a singleton object that lived
in the background page. Clarify where the object lives by accessing it
through a static method on the class.

Bug: None
Change-Id: I5b131e9a5679d27b6ad10dffc342c39ec9f75edc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1875383Reviewed-by: Akihiro Ota <akihiroota@chromium.org>
Commit-Queue: Anastasia Helfinstein <anastasi@google.com>
Cr-Commit-Position: refs/heads/master@{#709162}

chrome/browser/resources/chromeos/switch_access/background.js

@@ -2,9 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-/**
- * Initializes SwitchAccess and adds it to the extension's background page.
- *
- * @type {SwitchAccess}
- */
-window.switchAccess = new SwitchAccess();
+SwitchAccess.initialize();

chrome/browser/resources/chromeos/switch_access/menu_manager.js

@@ -128,7 +128,7 @@ class MenuManager {
    * @private
    */
   init_() {
-    if (window.switchAccess.improvedTextInputEnabled()) {
+    if (SwitchAccess.get().improvedTextInputEnabled()) {
       chrome.clipboard.onClipboardDataChanged.addListener(
           this.updateClipboardHasData.bind(this));
     }
@@ -243,7 +243,7 @@ class MenuManager {
 
     const autoNode = this.menuOriginNode_.automationNode;
     if (autoNode && !shouldReloadMenu &&
-        window.switchAccess.improvedTextInputEnabled()) {
+        SwitchAccess.get().improvedTextInputEnabled()) {
       const callback = this.reloadMenuForSelectionChange_.bind(this);
 
       autoNode.addEventListener(
@@ -516,7 +516,7 @@ class MenuManager {
     // Add text editing and navigation options.
     // TODO(anastasi): Move these actions into the node.
     const autoNode = node.automationNode;
-    if (autoNode && window.switchAccess.improvedTextInputEnabled() &&
+    if (autoNode && SwitchAccess.get().improvedTextInputEnabled() &&
         SwitchAccessPredicate.isTextInput(autoNode) &&
         autoNode.state[StateType.FOCUSED]) {
       actions.push(SAConstants.MenuAction.MOVE_CURSOR);

chrome/browser/resources/chromeos/switch_access/navigation_manager.js

@@ -251,7 +251,7 @@ class NavigationManager {
 
   /** @private */
   init_() {
-    if (window.switchAccess.prefsAreReady()) {
+    if (SwitchAccess.get().prefsAreReady()) {
       this.onPrefsReady();
     }
 
@@ -354,6 +354,6 @@ class NavigationManager {
     this.node_ = node;
     this.node_.onFocus();
     this.focusRingManager_.setFocusNodes(this.node_, this.group_);
-    window.switchAccess.restartAutoScan();
+    SwitchAccess.get().restartAutoScan();
   }
 }

chrome/browser/resources/chromeos/switch_access/nodes/back_button_node.js

@@ -18,7 +18,7 @@ class BackButtonNode extends SAChildNode {
     this.group_ = group;
 
     /** @private {chrome.automation.AutomationNode} */
-    this.node_ = window.switchAccess.getBackButtonAutomationNode();
+    this.node_ = SwitchAccess.get().getBackButtonAutomationNode();
   }
 
   /** @override */

chrome/browser/resources/chromeos/switch_access/switch_access.js

@@ -7,6 +7,15 @@
  * @implements {SwitchAccessInterface}
  */
 class SwitchAccess {
+  static initialize() {
+    window.switchAccess = new SwitchAccess();
+  }
+
+  static get() {
+    return window.switchAccess;
+  }
+
+  /** @private */
   constructor() {
     console.log('Switch access is enabled');