mash: Migrate ShelfLockingManager to ash/common.

ash/common/wm_shell.cc

Index: ash/common/wm_shell.cc
diff --git a/ash/common/wm_shell.cc b/ash/common/wm_shell.cc
index cf87b86c42e8e718a1189627417a3a9c159ab4ff..c4abb502add981b578484a79fd605283f7c946f9 100644
--- a/ash/common/wm_shell.cc
+++ b/ash/common/wm_shell.cc
@@ -82,6 +82,19 @@ void WmShell::RemoveShellObserver(ShellObserver* observer) {
   shell_observers_.RemoveObserver(observer);
 }
 
+void WmShell::OnLockStateEvent(LockStateObserver::EventType event) {
+  FOR_EACH_OBSERVER(LockStateObserver, lock_state_observers_,
+                    OnLockStateEvent(event));
+}
+
+void WmShell::AddLockStateObserver(LockStateObserver* observer) {
+  lock_state_observers_.AddObserver(observer);
+}
+
+void WmShell::RemoveLockStateObserver(LockStateObserver* observer) {
+  lock_state_observers_.RemoveObserver(observer);
+}
+
 WmShell::WmShell(std::unique_ptr<ShellDelegate> shell_delegate)
     : delegate_(std::move(shell_delegate)),
       focus_cycler_(new FocusCycler),