Fix the typo "visibility".

ash/wm/lock_state_controller_unittest.cc

Index: ash/wm/lock_state_controller_unittest.cc
diff --git a/ash/wm/lock_state_controller_unittest.cc b/ash/wm/lock_state_controller_unittest.cc
index fa2485654b8c6dda55612186c2252b7e24ee9d94..a9a13875b7be687a8835ea384cc44ddc4d5a8aca 100644
--- a/ash/wm/lock_state_controller_unittest.cc
+++ b/ash/wm/lock_state_controller_unittest.cc
@@ -960,7 +960,7 @@ TEST_F(LockStateControllerTest, TestHiddenBackgroundLockCancel) {
   Advance(SessionStateAnimator::ANIMATION_SPEED_UNDO_MOVE_WINDOWS);
 
   // When the CancelPrelockAnimation sequence finishes it queues up a
-  // restore background visibilty sequence when the background is hidden.
+  // restore background visibility sequence when the background is hidden.
   ExpectRestoringBackgroundVisibility();
 
   Advance(SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);
@@ -1010,7 +1010,7 @@ TEST_F(LockStateControllerTest, TestHiddenBackgroundLockUnlock) {
   Advance(SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS);
 
   // When the StartUnlockAnimationAfterUIDestroyed sequence finishes it queues
-  // up a restore background visibilty sequence when the background is hidden.
+  // up a restore background visibility sequence when the background is hidden.
   ExpectRestoringBackgroundVisibility();
 
   Advance(SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);