mash: Shell ref clean up for screen lock

ash/public/interfaces/session_controller.mojom

Index: ash/public/interfaces/session_controller.mojom
diff --git a/ash/public/interfaces/session_controller.mojom b/ash/public/interfaces/session_controller.mojom
index fbebb372a82b114c0760a278728d10b400e10def..246b2ba93c35fa95b51bc2b06ff8f7ba8ffc7c84 100644
--- a/ash/public/interfaces/session_controller.mojom
+++ b/ash/public/interfaces/session_controller.mojom
@@ -153,13 +153,17 @@ interface SessionController {
   SetUserSessionOrder(array<uint32> user_session_ids);
 
   // Runs the pre-lock animation to start locking ash. When the call returns,
-  // |locked| == true means that the post-lock animation is finished and ash is
-  // fully locked. Otherwise |locked| is false, which means something is wrong
-  // for the lock and ash is not locked. When the call returns with a true
+  // |locked| == true means that the ash post-lock animation is finished and ash
+  // is fully locked. Otherwise |locked| is false, which means something is
+  // wrong for the lock and ash is not locked. When the call returns with a true
   // |locked|, screen locker runs the post lock jobs such as a11y announcement
   // etc. Invoked by the screen locker during initialization.
   StartLock() => (bool locked);
 
+  // Notifies ash that chrome lock animations are finished. This is the last
+  // event for locking. SessionController forwards it to PowerEventObserver.
+  NotifyChromeLockAnimationsComplete();
+
   // Runs the pre-unlock animation. Invoked by the screen locker before
   // dismissing. When the mojo call returns, screen locker takes that as a
   // signal of finished unlock animation and dismisses itself.