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

chrome/browser/chromeos/accessibility/event_handler_common.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_EVENT_HANDLER_COMMON_H_
+#define CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_EVENT_HANDLER_COMMON_H_
+
+#include "extensions/browser/extension_host.h"
+#include "ui/events/event_handler.h"
+
+namespace chromeos {
+
+// Gets the extension host for the corresponding extension ID.
+extensions::ExtensionHost* GetAccessibilityExtensionHost(
+    const std::string& extension_id);
+
+// Forwards the key event to the extension background page for the
+// corresponding host.
+void ForwardKeyToExtension(const ui::KeyEvent& key_event,
+                           extensions::ExtensionHost* host);
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_ACCESSIBILITY_EVENT_HANDLER_COMMON_H_