mash: Run pre-unlock animation via SessionController

ash/session/session_controller.h

Index: ash/session/session_controller.h
diff --git a/ash/session/session_controller.h b/ash/session/session_controller.h
index b45a08d167f347ca235a62ea9870bc1d551e6d92..975e2185c461e5e85849fc1acc368ac8e5f8accd 100644
--- a/ash/session/session_controller.h
+++ b/ash/session/session_controller.h
@@ -104,6 +104,7 @@ class ASH_EXPORT SessionController
   void UpdateUserSession(mojom::UserSessionPtr user_session) override;
   void SetUserSessionOrder(
       const std::vector<uint32_t>& user_session_order) override;
+  void RunUnlockAnimation(const RunUnlockAnimationCallback& callback) override;
 
   // Test helpers.
   void ClearUserSessionsForTest();
@@ -148,6 +149,10 @@ class ASH_EXPORT SessionController
   // Last known login status. Used to track login status changes.
   LoginStatus login_status_ = LoginStatus::NOT_LOGGED_IN;
 
+  // Whether unlocking is in progress. The flag is set when the pre-unlock
+  // animation starts and reset when session state is no longer LOCKED.
+  bool is_unlocking_ = false;
+
   base::ObserverList<ash::SessionStateObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionController);