Promotes more accessors from WmShell to Shell

ash/common/system/tray_accessibility.cc

Index: ash/common/system/tray_accessibility.cc
diff --git a/ash/common/system/tray_accessibility.cc b/ash/common/system/tray_accessibility.cc
index 2e79edeeb35ec608a809a003bcbf6b5d2f75d2a5..7523dfe21cebb871ab5d7fd12d0a83bfee5c7c90 100644
--- a/ash/common/system/tray_accessibility.cc
+++ b/ash/common/system/tray_accessibility.cc
@@ -334,11 +334,11 @@ TrayAccessibility::TrayAccessibility(SystemTray* system_tray)
       previous_accessibility_state_(GetAccessibilityState()),
       show_a11y_menu_on_lock_screen_(true) {
   DCHECK(system_tray);
-  WmShell::Get()->system_tray_notifier()->AddAccessibilityObserver(this);
+  Shell::Get()->system_tray_notifier()->AddAccessibilityObserver(this);
 }
 
 TrayAccessibility::~TrayAccessibility() {
-  WmShell::Get()->system_tray_notifier()->RemoveAccessibilityObserver(this);
+  Shell::Get()->system_tray_notifier()->RemoveAccessibilityObserver(this);
 }
 
 void TrayAccessibility::SetTrayIconVisible(bool visible) {