Set keys to traverse accessibility tree. Using focus ring to highlight selected node.

chrome/browser/chromeos/accessibility/accessibility_manager.cc

Index: chrome/browser/chromeos/accessibility/accessibility_manager.cc
diff --git a/chrome/browser/chromeos/accessibility/accessibility_manager.cc b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
index 6cc9829594b5030fdf612322a72355a6ccc28261..9e25cb6b3568105513850bdf103ed7ff5e38d46c 100644
--- a/chrome/browser/chromeos/accessibility/accessibility_manager.cc
+++ b/chrome/browser/chromeos/accessibility/accessibility_manager.cc
@@ -41,6 +41,7 @@
 #include "chrome/browser/chromeos/accessibility/accessibility_highlight_manager.h"
 #include "chrome/browser/chromeos/accessibility/magnification_manager.h"
 #include "chrome/browser/chromeos/accessibility/select_to_speak_event_handler.h"
+#include "chrome/browser/chromeos/accessibility/switch_access_event_handler.h"
 #include "chrome/browser/chromeos/app_mode/kiosk_app_manager.h"
 #include "chrome/browser/chromeos/policy/browser_policy_connector_chromeos.h"
 #include "chrome/browser/chromeos/profiles/profile_helper.h"
@@ -940,8 +941,11 @@ void AccessibilityManager::UpdateSwitchAccessFromPref() {
 
   if (enabled) {
     switch_access_loader_->Load(profile_, base::Closure() /* done_cb */);
+    switch_access_event_handler_.reset(
+        new chromeos::SwitchAccessEventHandler());
   } else {
     switch_access_loader_->Unload();
+    switch_access_event_handler_.reset(nullptr);
   }
 }