Simplify VirtualKeyboardTray

ash/common/keyboard/keyboard_ui.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 "ash/common/keyboard/keyboard_ui.h"
 
 #include "ash/common/accessibility_delegate.h"
 #include "ash/common/keyboard/keyboard_ui_observer.h"
 #include "ash/common/system/accessibility_observer.h"
 #include "ash/common/system/tray/system_tray_notifier.h"
 #include "ash/common/system/tray_accessibility.h"
 #include "ash/common/wm_shell.h"
 #include "base/memory/ptr_util.h"
 #include "ui/keyboard/keyboard_controller.h"
 
 namespace ash {
 
 class KeyboardUIImpl : public KeyboardUI, public AccessibilityObserver {
  public:
-  KeyboardUIImpl() {
+  KeyboardUIImpl() : enabled_(false) {
     WmShell::Get()->system_tray_notifier()->AddAccessibilityObserver(this);
   }
 
   ~KeyboardUIImpl() override {
     if (WmShell::HasInstance() && WmShell::Get()->system_tray_notifier())
       WmShell::Get()->system_tray_notifier()->RemoveAccessibilityObserver(this);
   }
 
   // KeyboardUI:
   void Show() override {
     keyboard::KeyboardController::GetInstance()->ShowKeyboard(true);
   }
   void Hide() override {
     // Do nothing as this is called from ash::Shell, which also calls through
     // to the appropriate keyboard functions.
   }
   bool IsEnabled() override {
     return WmShell::Get()->accessibility_delegate()->IsVirtualKeyboardEnabled();
   }
 
   // AccessibilityObserver:
   void OnAccessibilityModeChanged(
       AccessibilityNotificationVisibility notify) override {
+    bool enabled = IsEnabled();
+    if (enabled_ == enabled)
+      return;
+
+    enabled_ = enabled;
     FOR_EACH_OBSERVER(KeyboardUIObserver, *observers(),
-                      OnKeyboardEnabledStateChanged(IsEnabled()));
+                      OnKeyboardEnabledStateChanged(enabled));
   }
 
  private:
+  bool enabled_;
+
   DISALLOW_COPY_AND_ASSIGN(KeyboardUIImpl);
 };
 
 KeyboardUI::~KeyboardUI() {}
 
 // static
 std::unique_ptr<KeyboardUI> KeyboardUI::Create() {
   return base::WrapUnique(new KeyboardUIImpl);
 }
 
 void KeyboardUI::AddObserver(KeyboardUIObserver* observer) {
   observers_.AddObserver(observer);
 }
 
 void KeyboardUI::RemoveObserver(KeyboardUIObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
 KeyboardUI::KeyboardUI() {}
 
 }  // namespace ash