Convert TrayAccessibility to wm common types

ash/system/tray/system_tray_notifier.cc

Index: ash/system/tray/system_tray_notifier.cc
diff --git a/ash/system/tray/system_tray_notifier.cc b/ash/system/tray/system_tray_notifier.cc
index 43b3bc48455f82ae71b77f0b473d641af376842c..d24444cd23eb3676be0854e4c6a525f8c54257d4 100644
--- a/ash/system/tray/system_tray_notifier.cc
+++ b/ash/system/tray/system_tray_notifier.cc
@@ -12,16 +12,6 @@ SystemTrayNotifier::SystemTrayNotifier() {
 SystemTrayNotifier::~SystemTrayNotifier() {
 }
 
-void SystemTrayNotifier::AddAccessibilityObserver(
-    AccessibilityObserver* observer) {
-  accessibility_observers_.AddObserver(observer);
-}
-
-void SystemTrayNotifier::RemoveAccessibilityObserver(
-    AccessibilityObserver* observer) {
-  accessibility_observers_.RemoveObserver(observer);
-}
-
 void SystemTrayNotifier::AddAudioObserver(AudioObserver* observer) {
   audio_observers_.AddObserver(observer);
 }
@@ -171,14 +161,6 @@ void SystemTrayNotifier::RemoveVirtualKeyboardObserver(
 }
 #endif
 
-void SystemTrayNotifier::NotifyAccessibilityModeChanged(
-    ui::AccessibilityNotificationVisibility notify) {
-  FOR_EACH_OBSERVER(
-      AccessibilityObserver,
-      accessibility_observers_,
-      OnAccessibilityModeChanged(notify));
-}
-
 void SystemTrayNotifier::NotifyAudioOutputVolumeChanged(uint64_t node_id,
                                                         double volume) {
   FOR_EACH_OBSERVER(AudioObserver, audio_observers_,