Use keys 1 through 3 to switch between and click on focusable elements.

chrome/browser/chromeos/accessibility/switch_access_event_handler.cc

 // 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.
 
 #include "chrome/browser/chromeos/accessibility/switch_access_event_handler.h"
 
 #include "ash/shell.h"
 #include "base/logging.h"
 #include "chrome/browser/chromeos/accessibility/accessibility_manager.h"
 #include "chrome/browser/chromeos/accessibility/event_handler_common.h"
@@ skipping 12 matching lines @@
   if (ash::Shell::HasInstance())
     ash::Shell::GetInstance()->RemovePreTargetHandler(this);
 }
 
 void SwitchAccessEventHandler::OnKeyEvent(ui::KeyEvent* event) {
   DCHECK(event);
 
   ui::KeyboardCode key_code = event->key_code();
   if (key_code == ui::VKEY_1 || key_code == ui::VKEY_2 ||
       key_code == ui::VKEY_3 || key_code == ui::VKEY_4 ||
-      key_code == ui::VKEY_5) {
+      key_code == ui::VKEY_5 || key_code == ui::VKEY_6 ||
+      key_code == ui::VKEY_7 || key_code == ui::VKEY_8 ||
+      key_code == ui::VKEY_9) {
     CancelEvent(event);
     LOG(ERROR) << "Dispatching key " << key_code - ui::VKEY_0
                << " to switch access";
     DispatchKeyEventToSwitchAccess(*event);
   }
 }
 
 void SwitchAccessEventHandler::CancelEvent(ui::Event* event) {
   DCHECK(event);
   if (event->cancelable()) {
     event->SetHandled();
     event->StopPropagation();
   }
 }
 
 void SwitchAccessEventHandler::DispatchKeyEventToSwitchAccess(
     const ui::KeyEvent& event) {
   extensions::ExtensionHost* host =
       GetAccessibilityExtensionHost(extension_misc::kSwitchAccessExtensionId);
   ForwardKeyToExtension(event, host);
 }
 
 }  // namespace chromeos