chromeos: Convert system tray session length limit to mojo

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 6eb56b358688a8ac8509d9ee4a93e7a91af26720..661c9f63cb921d236e155c5b0837ca9b5d55cd96 100644
--- a/ash/system/tray/system_tray_notifier.cc
+++ b/ash/system/tray/system_tray_notifier.cc
@@ -15,7 +15,6 @@
 #include "ash/system/screen_security/screen_share_observer.h"
 #include "ash/system/session/last_window_closed_observer.h"
 #include "ash/system/session/logout_button_observer.h"
-#include "ash/system/session/session_length_limit_observer.h"
 #include "ash/system/status_area_focus_observer.h"
 #include "ash/system/tray_tracing.h"
 #include "ash/system/virtual_keyboard/virtual_keyboard_observer.h"
@@ -229,26 +228,6 @@ void SystemTrayNotifier::NotifyScreenShareStop() {
     observer.OnScreenShareStop();
 }
 
-void SystemTrayNotifier::AddSessionLengthLimitObserver(
-    SessionLengthLimitObserver* observer) {
-  session_length_limit_observers_.AddObserver(observer);
-}
-
-void SystemTrayNotifier::RemoveSessionLengthLimitObserver(
-    SessionLengthLimitObserver* observer) {
-  session_length_limit_observers_.RemoveObserver(observer);
-}
-
-void SystemTrayNotifier::NotifySessionStartTimeChanged() {
-  for (auto& observer : session_length_limit_observers_)
-    observer.OnSessionStartTimeChanged();
-}
-
-void SystemTrayNotifier::NotifySessionLengthLimitChanged() {
-  for (auto& observer : session_length_limit_observers_)
-    observer.OnSessionLengthLimitChanged();
-}
-
 void SystemTrayNotifier::AddStatusAreaFocusObserver(
     StatusAreaFocusObserver* observer) {
   status_area_focus_observers_.AddObserver(observer);