Added auto-scan, made some small changes to how prefs are stored, refactored.

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

Index: chrome/browser/resources/chromeos/switch_access/testable_tree_walker.js
diff --git a/chrome/browser/resources/chromeos/switch_access/testable_switch_access.js b/chrome/browser/resources/chromeos/switch_access/testable_tree_walker.js
similarity index 67%
rename from chrome/browser/resources/chromeos/switch_access/testable_switch_access.js
rename to chrome/browser/resources/chromeos/switch_access/testable_tree_walker.js
index c5cdde736627254bd5b0ed86d0aea4e907974889..47470e4606524dff2fa361c604d2143d3eab64d8 100644
--- a/chrome/browser/resources/chromeos/switch_access/testable_switch_access.js
+++ b/chrome/browser/resources/chromeos/switch_access/testable_tree_walker.js
@@ -3,16 +3,15 @@
 // found in the LICENSE file.
 
 /**
- * Subclass of SwitchAccess that exposes SwitchAccess's methods for testing.
+ * Subclass of AutomationTreeWalker that exposes AutomationTreeWalker's methods
+ * for testing.
  */
-let TestableSwitchAccess = function() {
-  SwitchAccess.call(this);
+let TestableTreeWalker = function() {
+  AutomationTreeWalker.call(this);
 };
 
-TestableSwitchAccess.prototype = {
-  __proto__: SwitchAccess.prototype,
-
-  init_: function() {},
+TestableTreeWalker.prototype = {
+  __proto__: AutomationTreeWalker.prototype,
 
   getNextNode: function(node) {
     return this.getNextNode_(node);