Fix black background when locking with fullscreen window:

ash/wm/session_state_controller_impl2.cc

Index: ash/wm/session_state_controller_impl2.cc
diff --git a/ash/wm/session_state_controller_impl2.cc b/ash/wm/session_state_controller_impl2.cc
index 8b19827738b8c4faf5ba24b2ec5be5497c1c128f..8783e9e4367dac75c0efd34937da6bb4f1d70e67 100644
--- a/ash/wm/session_state_controller_impl2.cc
+++ b/ash/wm/session_state_controller_impl2.cc
@@ -11,7 +11,9 @@
 #include "ash/wm/session_state_animator.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
+#include "base/timer.h"
 #include "ui/aura/root_window.h"
+#include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/views/corewm/compound_event_filter.h"
 
 #if defined(OS_CHROMEOS)
@@ -20,6 +22,34 @@
 
 namespace ash {
 
+namespace {
+
+aura::Window* GetBackground() {
+  aura::RootWindow* root_window = Shell::GetPrimaryRootWindow();
+  return Shell::GetContainer(root_window,
+      internal::kShellWindowId_DesktopBackgroundContainer);
+}
+
+bool IsBackgroundHidden() {
+  return !GetBackground()->IsVisible();
+}
+
+void ShowBackground() {
+  ui::ScopedLayerAnimationSettings settings(
+      GetBackground()->layer()->GetAnimator());
+  settings.SetTransitionDuration(base::TimeDelta());
+  GetBackground()->Show();
+}
+
+void HideBackground() {
+  ui::ScopedLayerAnimationSettings settings(
+      GetBackground()->layer()->GetAnimator());
+  settings.SetTransitionDuration(base::TimeDelta());
+  GetBackground()->Hide();
+}
+
+} // namespace
+
 SessionStateControllerImpl2::TestApi::TestApi(
     SessionStateControllerImpl2* controller)
     : controller_(controller) {
@@ -32,7 +62,9 @@ SessionStateControllerImpl2::SessionStateControllerImpl2()
     : login_status_(user::LOGGED_IN_NONE),
       system_is_locked_(false),
       shutting_down_(false),
-      shutdown_after_lock_(false) {
+      shutdown_after_lock_(false),
+      animating_lock_(false),
+      undoable_lock_animation_(false) {
   Shell::GetPrimaryRootWindow()->AddRootWindowObserver(this);
 }
 
@@ -50,6 +82,7 @@ void SessionStateControllerImpl2::OnLoginStateChanged(
 void SessionStateControllerImpl2::OnAppTerminating() {
   // If we hear that Chrome is exiting but didn't request it ourselves, all we
   // can really hope for is that we'll have time to clear the screen.
+  // This is also a case when user signs off.
   if (!shutting_down_) {
     shutting_down_ = true;
     Shell* shell = ash::Shell::GetInstance();
@@ -69,22 +102,10 @@ void SessionStateControllerImpl2::OnLockStateChanged(bool locked) {
   system_is_locked_ = locked;
 
   if (locked) {
-    base::Callback<void(void)> callback =
-        base::Bind(&SessionStateControllerImpl2::OnLockScreenAnimationFinished,
-        base::Unretained(this));
-    animator_->StartAnimationWithCallback(
-        internal::SessionStateAnimator::LOCK_SCREEN_CONTAINERS,
-        internal::SessionStateAnimator::ANIMATION_RAISE_TO_SCREEN,
-        internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
-        callback);
-    lock_timer_.Stop();
+    StartLockAnimationPhaseTwo();
     lock_fail_timer_.Stop();
   } else {
-    animator_->StartAnimation(
-        internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS |
-        internal::SessionStateAnimator::LAUNCHER,
-        internal::SessionStateAnimator::ANIMATION_DROP,
-        internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS);
+    StartUnlockAnimationPhaseTwo();
   }
 }
 
@@ -93,68 +114,27 @@ void SessionStateControllerImpl2::SetLockScreenDisplayedCallback(
   lock_screen_displayed_callback_ = callback;
 }
 
-void SessionStateControllerImpl2::OnLockScreenAnimationFinished() {
-  FOR_EACH_OBSERVER(SessionStateObserver, observers_,
-      OnSessionStateEvent(
-          SessionStateObserver::EVENT_LOCK_ANIMATION_FINISHED));
-  if (!lock_screen_displayed_callback_.is_null()) {
-    lock_screen_displayed_callback_.Run();
-    lock_screen_displayed_callback_.Reset();
-  }
-  if (shutdown_after_lock_) {
-    shutdown_after_lock_ = false;
-    StartLockToShutdownTimer();
-  }
-}
-
 void SessionStateControllerImpl2::OnStartingLock() {
   if (shutting_down_ || system_is_locked_)
     return;
-
-  animator_->StartAnimation(
-      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS |
-      internal::SessionStateAnimator::LAUNCHER,
-      internal::SessionStateAnimator::ANIMATION_LIFT,
-      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS);
-  FOR_EACH_OBSERVER(SessionStateObserver, observers_,
-      OnSessionStateEvent(SessionStateObserver::EVENT_LOCK_ANIMATION_STARTED));
-  // Hide the screen locker containers so we can raise them later.
-  animator_->StartAnimation(
-      internal::SessionStateAnimator::LOCK_SCREEN_CONTAINERS,
-      internal::SessionStateAnimator::ANIMATION_HIDE_IMMEDIATELY,
-      internal::SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);
+  if (animating_lock_)
+    return;
+  StartImmediateLockAnimationPhaseOne();
 }
 
 void SessionStateControllerImpl2::StartLockAnimationAndLockImmediately() {
-  animator_->StartAnimation(
-      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS |
-      internal::SessionStateAnimator::LAUNCHER,
-      internal::SessionStateAnimator::ANIMATION_LIFT,
-      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS);
-  FOR_EACH_OBSERVER(SessionStateObserver, observers_,
-      OnSessionStateEvent(SessionStateObserver::EVENT_LOCK_ANIMATION_STARTED));
-  OnLockTimeout();
+  if (animating_lock_)
+    return;
+  StartImmediateLockAnimationPhaseOne();
 }
 
 void SessionStateControllerImpl2::StartLockAnimation(bool shutdown_after_lock) {
+  if (animating_lock_)
+    return;
   shutdown_after_lock_ = shutdown_after_lock;
+  undoable_lock_animation_ = true;
 
-  animator_->StartAnimation(
-      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS |
-      internal::SessionStateAnimator::LAUNCHER,
-      internal::SessionStateAnimator::ANIMATION_LIFT,
-      internal::SessionStateAnimator::ANIMATION_SPEED_UNDOABLE);
-  FOR_EACH_OBSERVER(SessionStateObserver, observers_,
-      OnSessionStateEvent(
-          SessionStateObserver::EVENT_PRELOCK_ANIMATION_STARTED));
-  StartLockTimer();
-}
-
-void SessionStateControllerImpl2::StartShutdownAnimation() {
-  animator_->StartGlobalAnimation(
-      internal::SessionStateAnimator::ANIMATION_GRAYSCALE_BRIGHTNESS,
-      internal::SessionStateAnimator::ANIMATION_SPEED_SHUTDOWN);
-  StartPreShutdownAnimationTimer();
+  StartUndoableLockAnimationPhaseOne();
 }
 
 bool SessionStateControllerImpl2::LockRequested() {
@@ -166,19 +146,15 @@ bool SessionStateControllerImpl2::ShutdownRequested() {
 }
 
 bool SessionStateControllerImpl2::CanCancelLockAnimation() {
-  return lock_timer_.IsRunning();
+  return undoable_lock_animation_;
 }
 
 void SessionStateControllerImpl2::CancelLockAnimation() {
   if (!CanCancelLockAnimation())
     return;
   shutdown_after_lock_ = false;
-  animator_->StartAnimation(
-      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS |
-      internal::SessionStateAnimator::LAUNCHER,
-      internal::SessionStateAnimator::ANIMATION_DROP,
-      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS);
-  lock_timer_.Stop();
+  animating_lock_ = false;
+  UndoLockAnimationPhaseOne();
 }
 
 bool SessionStateControllerImpl2::CanCancelShutdownAnimation() {
@@ -187,6 +163,10 @@ bool SessionStateControllerImpl2::CanCancelShutdownAnimation() {
          lock_to_shutdown_timer_.IsRunning();
 }
 
+void SessionStateControllerImpl2::StartShutdownAnimation() {
+  StartCancellableShutdownAnimation();
+}
+
 void SessionStateControllerImpl2::CancelShutdownAnimation() {
   if (!CanCancelShutdownAnimation())
     return;
@@ -217,10 +197,7 @@ void SessionStateControllerImpl2::RequestShutdownImpl() {
   shell->env_filter()->set_cursor_hidden_by_filter(false);
   shell->cursor_manager()->ShowCursor(false);
 
-  animator_->StartGlobalAnimation(
-      internal::SessionStateAnimator::ANIMATION_GRAYSCALE_BRIGHTNESS,
-      internal::SessionStateAnimator::ANIMATION_SPEED_SHUTDOWN);
-  StartRealShutdownTimer();
+  StartShutdownAnimationImpl();
 }
 
 void SessionStateControllerImpl2::OnRootWindowHostCloseRequested(
@@ -228,31 +205,10 @@ void SessionStateControllerImpl2::OnRootWindowHostCloseRequested(
   Shell::GetInstance()->delegate()->Exit();
 }
 
-void SessionStateControllerImpl2::StartLockTimer() {
-  lock_timer_.Stop();
-  lock_timer_.Start(
-      FROM_HERE,
-      animator_->GetDuration(
-          internal::SessionStateAnimator::ANIMATION_SPEED_UNDOABLE),
-      this, &SessionStateControllerImpl2::OnLockTimeout);
-}
-
-void SessionStateControllerImpl2::OnLockTimeout() {
-  delegate_->RequestLockScreen();
-  lock_fail_timer_.Start(
-      FROM_HERE,
-      base::TimeDelta::FromMilliseconds(kLockFailTimeoutMs),
-      this, &SessionStateControllerImpl2::OnLockFailTimeout);
-}
-
 void SessionStateControllerImpl2::OnLockFailTimeout() {
   DCHECK(!system_is_locked_);
   // Undo lock animation.
-  animator_->StartAnimation(
-      internal::SessionStateAnimator::LAUNCHER |
-      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS,
-      internal::SessionStateAnimator::ANIMATION_DROP,
-      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS);
+  StartUnlockAnimationPhaseTwo();
 }
 
 void SessionStateControllerImpl2::StartLockToShutdownTimer() {
@@ -264,30 +220,52 @@ void SessionStateControllerImpl2::StartLockToShutdownTimer() {
       this, &SessionStateControllerImpl2::OnLockToShutdownTimeout);
 }
 
-
 void SessionStateControllerImpl2::OnLockToShutdownTimeout() {
   DCHECK(system_is_locked_);
-  StartShutdownAnimation();
+  StartCancellableShutdownAnimation();
+}
+
+void SessionStateControllerImpl2::StartCancellableShutdownAnimation() {
+  animator_->StartGlobalAnimation(
+      internal::SessionStateAnimator::ANIMATION_GRAYSCALE_BRIGHTNESS,
+      internal::SessionStateAnimator::ANIMATION_SPEED_SHUTDOWN);
+  StartPreShutdownAnimationTimer();
+}
+
+void SessionStateControllerImpl2::StartShutdownAnimationImpl() {
+  animator_->StartGlobalAnimation(
+      internal::SessionStateAnimator::ANIMATION_GRAYSCALE_BRIGHTNESS,
+      internal::SessionStateAnimator::ANIMATION_SPEED_SHUTDOWN);
+  StartRealShutdownTimer(true);
 }
 
 void SessionStateControllerImpl2::StartPreShutdownAnimationTimer() {
   pre_shutdown_timer_.Stop();
   pre_shutdown_timer_.Start(
       FROM_HERE,
-      base::TimeDelta::FromMilliseconds(kShutdownTimeoutMs),
+      animator_->
+          GetDuration(internal::SessionStateAnimator::ANIMATION_SPEED_SHUTDOWN),
       this, &SessionStateControllerImpl2::OnPreShutdownAnimationTimeout);
 }
 
 void SessionStateControllerImpl2::OnPreShutdownAnimationTimeout() {
-  if (!shutting_down_)
-    RequestShutdownImpl();
+  shutting_down_ = true;
+
+  Shell* shell = ash::Shell::GetInstance();
+  shell->env_filter()->set_cursor_hidden_by_filter(false);
+  shell->cursor_manager()->ShowCursor(false);
+
+  StartRealShutdownTimer(false);
 }
 
-void SessionStateControllerImpl2::StartRealShutdownTimer() {
+
+void SessionStateControllerImpl2::StartRealShutdownTimer(bool animation_time) {
   base::TimeDelta duration =
       base::TimeDelta::FromMilliseconds(kShutdownRequestDelayMs);
-  duration += animator_->GetDuration(
-      internal::SessionStateAnimator::ANIMATION_SPEED_SHUTDOWN);
+  if (animation_time) {
+    duration += animator_->GetDuration(
+        internal::SessionStateAnimator::ANIMATION_SPEED_SHUTDOWN);
+  }
   real_shutdown_timer_.Start(
       FROM_HERE,
       duration,
@@ -310,6 +288,165 @@ void SessionStateControllerImpl2::OnRealShutdownTimeout() {
 
 void SessionStateControllerImpl2::OnLockScreenHide(
   base::Callback<void(void)>& callback) {
+  StartUnlockAnimationPhaseOne(callback);
+}
+
+void SessionStateControllerImpl2::LockAnimationUndone() {
+  undoable_lock_animation_ = false;
+  RestoreUnlockedProperties();
+}
+
+void SessionStateControllerImpl2::LockAnimationPhaseOneCompleted() {
+  undoable_lock_animation_ = false;
+
+  delegate_->RequestLockScreen();
+  lock_fail_timer_.Start(
+      FROM_HERE,
+      base::TimeDelta::FromMilliseconds(kLockFailTimeoutMs),
+      this, &SessionStateControllerImpl2::OnLockFailTimeout);
+}
+
+void SessionStateControllerImpl2::LockAnimationPhaseTwoCompleted() {
+  animating_lock_ = false;
+
+  FOR_EACH_OBSERVER(SessionStateObserver, observers_,
+      OnSessionStateEvent(
+          SessionStateObserver::EVENT_LOCK_ANIMATION_FINISHED));
+  if (!lock_screen_displayed_callback_.is_null()) {
+    lock_screen_displayed_callback_.Run();
+    lock_screen_displayed_callback_.Reset();
+  }
+  if (shutdown_after_lock_) {
+    shutdown_after_lock_ = false;
+    StartLockToShutdownTimer();
+  }
+}
+
+void SessionStateControllerImpl2::UnlockAnimationPhaseTwoCompleted() {
+  RestoreUnlockedProperties();
+}
+
+void SessionStateControllerImpl2::StartImmediateLockAnimationPhaseOne() {
+  animating_lock_ = true;
+
+  StoreUnlockedProperties();
+
+  base::Closure next_animation_starter =
+      base::Bind(&SessionStateControllerImpl2::LockAnimationPhaseOneCompleted,
+      base::Unretained(this));
+  ui::LayerAnimationObserver* observer =
+      new ui::AnimationFinishedObserver(next_animation_starter);
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS,
+      internal::SessionStateAnimator::ANIMATION_LIFT,
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::LAUNCHER,
+      internal::SessionStateAnimator::ANIMATION_FADE_OUT,
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+
+  // Hide the screen locker containers so we can raise them later.
+  animator_->StartAnimation(
+      internal::SessionStateAnimator::LOCK_SCREEN_CONTAINERS,
+      internal::SessionStateAnimator::ANIMATION_HIDE_IMMEDIATELY,
+      internal::SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);
+
+  AnimateBackgroundAppearanceIfNecessary(
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+
+  FOR_EACH_OBSERVER(SessionStateObserver, observers_,
+      OnSessionStateEvent(SessionStateObserver::EVENT_LOCK_ANIMATION_STARTED));
+}
+
+void SessionStateControllerImpl2::StartUndoableLockAnimationPhaseOne() {
+  animating_lock_ = true;
+  StoreUnlockedProperties();
+
+  base::Closure next_animation_starter =
+      base::Bind(&SessionStateControllerImpl2::LockAnimationPhaseOneCompleted,
+      base::Unretained(this));
+  ui::AnimationFinishedObserver* observer =
+      new ui::AnimationFinishedObserver(next_animation_starter);
+
+  observer->Pause();
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS,
+      internal::SessionStateAnimator::ANIMATION_LIFT,
+      internal::SessionStateAnimator::ANIMATION_SPEED_UNDOABLE,
+      observer);
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::LAUNCHER,
+      internal::SessionStateAnimator::ANIMATION_FADE_OUT,
+      internal::SessionStateAnimator::ANIMATION_SPEED_UNDOABLE,
+      observer);
+
+  // Hide the screen locker containers so we can raise them later.
+  animator_->StartAnimation(
+      internal::SessionStateAnimator::LOCK_SCREEN_CONTAINERS,
+      internal::SessionStateAnimator::ANIMATION_HIDE_IMMEDIATELY,
+      internal::SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);
+
+  AnimateBackgroundAppearanceIfNecessary(
+      internal::SessionStateAnimator::ANIMATION_SPEED_UNDOABLE,
+      observer);
+
+  FOR_EACH_OBSERVER(SessionStateObserver, observers_,
+      OnSessionStateEvent(
+          SessionStateObserver::EVENT_PRELOCK_ANIMATION_STARTED));
+  observer->Unpause();
+}
+
+void SessionStateControllerImpl2::UndoLockAnimationPhaseOne() {
+  base::Closure next_animation_starter =
+      base::Bind(&SessionStateControllerImpl2::LockAnimationUndone,
+      base::Unretained(this));
+  ui::AnimationFinishedObserver* observer =
+      new ui::AnimationFinishedObserver(next_animation_starter);
+
+  observer->Pause();
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS,
+      internal::SessionStateAnimator::ANIMATION_UNDO_LIFT,
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::LAUNCHER,
+      internal::SessionStateAnimator::ANIMATION_FADE_IN,
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+
+  AnimateBackgroundHidingIfNecessary(
+      internal::SessionStateAnimator::ANIMATION_SPEED_UNDOABLE,
+      observer);
+  observer->Unpause();
+}
+
+void SessionStateControllerImpl2::StartLockAnimationPhaseTwo() {
+  base::Closure next_animation_starter =
+      base::Bind(&SessionStateControllerImpl2::LockAnimationPhaseTwoCompleted,
+      base::Unretained(this));
+
+  ui::LayerAnimationObserver* observer =
+      new ui::AnimationFinishedObserver(next_animation_starter);
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::LOCK_SCREEN_CONTAINERS,
+      internal::SessionStateAnimator::ANIMATION_RAISE_TO_SCREEN,
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+}
+
+void SessionStateControllerImpl2::StartUnlockAnimationPhaseOne(
+    base::Closure& callback) {
   animator_->StartAnimationWithCallback(
       internal::SessionStateAnimator::LOCK_SCREEN_CONTAINERS,
       internal::SessionStateAnimator::ANIMATION_LIFT,
@@ -317,4 +454,84 @@ void SessionStateControllerImpl2::OnLockScreenHide(
       callback);
 }
 
+void SessionStateControllerImpl2::StartUnlockAnimationPhaseTwo() {
+  base::Closure next_animation_starter =
+      base::Bind(&SessionStateControllerImpl2::UnlockAnimationPhaseTwoCompleted,
+      base::Unretained(this));
+
+  ui::LayerAnimationObserver* observer =
+      new ui::AnimationFinishedObserver(next_animation_starter);
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::NON_LOCK_SCREEN_CONTAINERS,
+      internal::SessionStateAnimator::ANIMATION_DROP,
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+
+  animator_->StartAnimationWithObserver(
+      internal::SessionStateAnimator::LAUNCHER,
+      internal::SessionStateAnimator::ANIMATION_FADE_IN,
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+
+  AnimateBackgroundHidingIfNecessary(
+      internal::SessionStateAnimator::ANIMATION_SPEED_MOVE_WINDOWS,
+      observer);
+}
+
+void SessionStateControllerImpl2::StoreUnlockedProperties() {
+  if (!unlocked_properties_.get()) {
+    unlocked_properties_.reset(new UnlockedStateProperties());
+    unlocked_properties_->background_is_hidden = IsBackgroundHidden();
+  }
+  if (unlocked_properties_->background_is_hidden) {
+    // Hide background so that it can be animated later.
+    animator_->StartAnimation(
+        internal::SessionStateAnimator::DESKTOP_BACKGROUND,
+        internal::SessionStateAnimator::ANIMATION_HIDE_IMMEDIATELY,
+        internal::SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);
+    ShowBackground();
+  }
+}
+
+void SessionStateControllerImpl2::RestoreUnlockedProperties() {
+  if (!unlocked_properties_.get())
+    return;
+  if (unlocked_properties_->background_is_hidden) {
+    HideBackground();
+    // Restore background visibility.
+    animator_->StartAnimation(
+        internal::SessionStateAnimator::DESKTOP_BACKGROUND,
+        internal::SessionStateAnimator::ANIMATION_FADE_IN,
+        internal::SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);
+  }
+  unlocked_properties_.reset();
+}
+
+void SessionStateControllerImpl2::AnimateBackgroundAppearanceIfNecessary(
+    internal::SessionStateAnimator::AnimationSpeed speed,
+    ui::LayerAnimationObserver* observer) {
+  if (unlocked_properties_.get() &&
+      unlocked_properties_->background_is_hidden) {
+    animator_->StartAnimationWithObserver(
+        internal::SessionStateAnimator::DESKTOP_BACKGROUND,
+        internal::SessionStateAnimator::ANIMATION_FADE_IN,
+        speed,
+        observer);
+  }
+}
+
+void SessionStateControllerImpl2::AnimateBackgroundHidingIfNecessary(
+    internal::SessionStateAnimator::AnimationSpeed speed,
+    ui::LayerAnimationObserver* observer) {
+  if (unlocked_properties_.get() &&
+      unlocked_properties_->background_is_hidden) {
+    animator_->StartAnimationWithObserver(
+        internal::SessionStateAnimator::DESKTOP_BACKGROUND,
+        internal::SessionStateAnimator::ANIMATION_FADE_OUT,
+        speed,
+        observer);
+  }
+}
+
 }  // namespace ash