Use OnceCallback on Mojo interfaces in //ash

ash/session/session_controller.cc

Index: ash/session/session_controller.cc
diff --git a/ash/session/session_controller.cc b/ash/session/session_controller.cc
index a4edf2dbaa6627e03a1d2e76f38ef522fe58744f..82f5a6c5cf8c11c88a73f778c1082481080a501a 100644
--- a/ash/session/session_controller.cc
+++ b/ash/session/session_controller.cc
@@ -5,6 +5,7 @@
 #include "ash/session/session_controller.h"
 
 #include <algorithm>
+#include <utility>
 
 #include "ash/session/session_observer.h"
 #include "ash/shell.h"
@@ -239,9 +240,9 @@ void SessionController::SetUserSessionOrder(
   }
 }
 
-void SessionController::StartLock(const StartLockCallback& callback) {
+void SessionController::StartLock(StartLockCallback callback) {
   DCHECK(start_lock_callback_.is_null());
-  start_lock_callback_ = callback;
+  start_lock_callback_ = std::move(callback);
 
   LockStateController* const lock_state_controller =
       Shell::Get()->lock_state_controller();
@@ -257,12 +258,13 @@ void SessionController::NotifyChromeLockAnimationsComplete() {
 }
 
 void SessionController::RunUnlockAnimation(
-    const RunUnlockAnimationCallback& callback) {
+    RunUnlockAnimationCallback callback) {
   is_unlocking_ = true;
 
   // Shell could have no instance in tests.
   if (Shell::HasInstance())
-    Shell::Get()->lock_state_controller()->OnLockScreenHide(callback);
+    Shell::Get()->lock_state_controller()->OnLockScreenHide(
+        std::move(callback));
 }
 
 void SessionController::NotifyChromeTerminating() {