Remove GetOptionalAnimationDuration from home_scree_delegate

Last (only?) usage was removed in CL:2482042

BUG=1137452

Change-Id: I66c9a940c4fd182a99a322fa47eb3a17b0342a33
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2496187Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Toni Baržić <tbarzic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820885}

ash/app_list/app_list_controller_impl.cc

@@ -994,16 +994,6 @@ void AppListControllerImpl::UpdateScaleAndOpacityForHomeLauncher(
       std::move(callback));
 }
 
-base::Optional<base::TimeDelta>
-AppListControllerImpl::GetOptionalAnimationDuration() {
-  if (model_->state() == AppListState::kStateEmbeddedAssistant) {
-    // If Assistant is shown, we don't want any delay in animation transitions
-    // since the launcher is already shown.
-    return base::TimeDelta::Min();
-  }
-  return base::nullopt;
-}
-
 void AppListControllerImpl::Back() {
   presenter_.GetView()->Back();
 }

ash/app_list/app_list_controller_impl.h

@@ -285,7 +285,6 @@ class ASH_EXPORT AppListControllerImpl
       float opacity,
       base::Optional<AnimationInfo> animation_info,
       UpdateAnimationSettingsCallback callback) override;
-  base::Optional<base::TimeDelta> GetOptionalAnimationDuration() override;
   base::ScopedClosureRunner DisableHomeScreenBackgroundBlur() override;
   void OnHomeLauncherAnimationComplete(bool shown, int64_t display_id) override;
   void OnHomeLauncherPositionChanged(int percent_shown,

ash/home_screen/home_screen_delegate.h

@@ -75,10 +75,6 @@ class HomeScreenDelegate {
       base::Optional<AnimationInfo> animation_info,
       UpdateAnimationSettingsCallback callback) = 0;
 
-  // Returns an optional animation duration which is going to be used to set
-  // the transition animation if provided.
-  virtual base::Optional<base::TimeDelta> GetOptionalAnimationDuration() = 0;
-
   // True if home screen is visible.
   virtual bool IsHomeScreenVisible() = 0;