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

chrome/browser/chromeos/accessibility/accessibility_manager.h

Index: chrome/browser/chromeos/accessibility/accessibility_manager.h
diff --git a/chrome/browser/chromeos/accessibility/accessibility_manager.h b/chrome/browser/chromeos/accessibility/accessibility_manager.h
index c224c7322114f6fef356e7a3a79ce7f7257654c7..94ba83dbf29fddee9e9c231623391c38c39f5483 100644
--- a/chrome/browser/chromeos/accessibility/accessibility_manager.h
+++ b/chrome/browser/chromeos/accessibility/accessibility_manager.h
@@ -37,6 +37,7 @@ namespace chromeos {
 class AccessibilityExtensionLoader;
 class AccessibilityHighlightManager;
 class SelectToSpeakEventHandler;
+class SwitchAccessEventHandler;
 
 enum AccessibilityNotificationType {
   ACCESSIBILITY_MANAGER_SHUTDOWN,
@@ -421,6 +422,9 @@ class AccessibilityManager
 
   std::unique_ptr<AccessibilityExtensionLoader> switch_access_loader_;
 
+  std::unique_ptr<chromeos::SwitchAccessEventHandler>
+      switch_access_event_handler_;
+
   base::WeakPtrFactory<AccessibilityManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AccessibilityManager);