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

chrome/browser/chromeos/accessibility/select_to_speak_event_handler.cc

 // Copyright 2016 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/select_to_speak_event_handler.h"
 
 #include "ash/shell.h"
+#include "base/logging.h"
 #include "chrome/browser/speech/tts_controller.h"
 #include "chrome/browser/ui/aura/accessibility/automation_manager_aura.h"
 #include "content/public/browser/browser_thread.h"
 #include "ui/aura/window.h"
 #include "ui/display/display.h"
 #include "ui/events/event.h"
 #include "ui/views/focus/view_storage.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 
 namespace chromeos {
 
 SelectToSpeakEventHandler::SelectToSpeakEventHandler() {
   if (ash::Shell::HasInstance())
     ash::Shell::GetInstance()->AddPreTargetHandler(this);
 }
 
 SelectToSpeakEventHandler::~SelectToSpeakEventHandler() {
   if (ash::Shell::HasInstance())
     ash::Shell::GetInstance()->RemovePreTargetHandler(this);
 }
 
 void SelectToSpeakEventHandler::OnKeyEvent(ui::KeyEvent* event) {
+  DCHECK(event);
+
   // We can only call TtsController on the UI thread, make sure we
   // don't ever try to run this code on some other thread.
   CHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
   ui::KeyboardCode key_code = event->key_code();
 
   // Stop speech when the user taps and releases Control or Search
   // without pressing any other keys along the way.
   if (state_ != MOUSE_RELEASED && event->type() == ui::ET_KEY_RELEASED &&
       (key_code == ui::VKEY_CONTROL || key_code == ui::VKEY_LWIN) &&
@@ skipping 25 matching lines @@
         CancelEvent(event);
         state_ = INACTIVE;
       }
     }
   } else if (state_ == SEARCH_DOWN) {
     state_ = INACTIVE;
   }
 }
 
 void SelectToSpeakEventHandler::OnMouseEvent(ui::MouseEvent* event) {
+  DCHECK(event);
   if (state_ == INACTIVE)
     return;
 
   if ((state_ == SEARCH_DOWN || state_ == MOUSE_RELEASED) &&
       event->type() == ui::ET_MOUSE_PRESSED) {
     state_ = CAPTURING;
   }
 
   if (state_ == WAIT_FOR_MOUSE_RELEASE &&
       event->type() == ui::ET_MOUSE_RELEASED) {
@@ skipping 64 matching lines @@
       last_view_storage_id_ =
           views::ViewStorage::GetInstance()->CreateStorageID();
     }
     views::ViewStorage::GetInstance()->RemoveView(last_view_storage_id_);
     views::ViewStorage::GetInstance()->StoreView(last_view_storage_id_,
                                                  hit_view);
   }
 }
 
 void SelectToSpeakEventHandler::CancelEvent(ui::Event* event) {
+  DCHECK(event);
   if (event->cancelable()) {
     event->SetHandled();
     event->StopPropagation();
   }
 }
 
 void SelectToSpeakEventHandler::SendCancelAXEvent() {
   // If the user releases Search while the button is still down, cancel
   // the Select-to-speak gesture. Try to post it on the same View that
   // was last targeted, but if that's impossible, post it on the desktop.
   views::View* last_view =
       last_view_storage_id_
           ? views::ViewStorage::GetInstance()->RetrieveView(
                 last_view_storage_id_)
           : nullptr;
   if (last_view) {
     last_view->NotifyAccessibilityEvent(ui::AX_EVENT_MOUSE_CANCELED, true);
   } else {
     AutomationManagerAura::GetInstance()->HandleEvent(
         nullptr, nullptr, ui::AX_EVENT_MOUSE_CANCELED);
   }
 }
 
 }  // namespace chromeos