Revert "Cros: Add metrics for transitions in the hotseat"

This reverts commit 9256783c.

Reason for revert: This CL may be responsible for multiple All/Overview* flaky use-of-uninitialized-value.

First failed build:
https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/16416?blamelist=1#blamelist-tab

Because the original CL has been landed for few days, the change in
tools/metrics/histograms/histograms.xml are not reverted due to merge warning.

Original change's description:
> Cros: Add metrics for transitions in the hotseat
>
> Report animation smoothness for the transition into the hotseat in the
> HomeLauncher.
>
> Bug: 1022178, 1022177
> Change-Id: I5dc5e76688aa5a88bcabb5d688b419d819932867
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1917941
> Commit-Queue: Ana Salazar <anasalazar@chromium.org>
> Reviewed-by: Alex Newcomer <newcomer@chromium.org>
> Reviewed-by: Manu Cornet <manucornet@chromium.org>
> Reviewed-by: Nik Bhagat <nikunjb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#718266}

TBR=nikunjb@chromium.org,newcomer@chromium.org,manucornet@chromium.org,anasalazar@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1022178, 1022177, 1028255
Change-Id: If460f00f10fb8f8df2a9f7d3d41abfdd91f0ad0e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1933739
Commit-Queue: Owen Min <zmin@chromium.org>
Reviewed-by: Owen Min <zmin@chromium.org>
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718782}

ash/shelf/hotseat_transition_animator.cc

@@ -10,7 +10,6 @@
 #include "ash/shelf/shelf_widget.h"
 #include "ash/shell.h"
 #include "ash/wm/tablet_mode/tablet_mode_controller.h"
-#include "base/metrics/histogram_macros.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animator.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
@@ -20,40 +19,8 @@
 
 namespace ash {
 
-class HotseatTransitionAnimator::TransitionAnimationMetricsReporter
-    : public ui::AnimationMetricsReporter {
- public:
-  TransitionAnimationMetricsReporter() {}
-
-  ~TransitionAnimationMetricsReporter() override = default;
-
-  void animating_to_shown_hotseat(bool animating_to_shown_hotseat) {
-    animating_to_shown_hotseat_ = animating_to_shown_hotseat;
-  }
-
-  // ui::AnimationMetricsReporter:
-  void Report(int value) override {
-    if (animating_to_shown_hotseat_) {
-      UMA_HISTOGRAM_PERCENTAGE(
-          "Ash.HotseatTransition.AnimationSmoothness.TransitionToShownHotseat",
-          value);
-    } else {
-      UMA_HISTOGRAM_PERCENTAGE(
-          "Ash.HotseatTransition.AnimationSmoothness."
-          "TransitionFromShownHotseat",
-          value);
-    }
-  }
-
- private:
-  // Whether the animation reported is transitioning state into a shown hotseat.
-  bool animating_to_shown_hotseat_ = false;
-};
-
 HotseatTransitionAnimator::HotseatTransitionAnimator(ShelfWidget* shelf_widget)
-    : shelf_widget_(shelf_widget),
-      animation_metrics_reporter_(
-          std::make_unique<TransitionAnimationMetricsReporter>()) {
+    : shelf_widget_(shelf_widget) {
   Shell::Get()->tablet_mode_controller()->AddObserver(this);
 }
 
@@ -153,8 +120,6 @@ void HotseatTransitionAnimator::SetAnimationStartProperties(
                                : shelf_widget_->hotseat_widget()
                                      ->GetOpaqueBackground()
                                      ->rounded_corner_radii());
-  animation_metrics_reporter_->animating_to_shown_hotseat(new_state ==
-                                                          HotseatState::kShown);
 }
 
 void HotseatTransitionAnimator::StartAnimation(HotseatState old_state,
@@ -167,8 +132,6 @@ void HotseatTransitionAnimator::StartAnimation(HotseatState old_state,
   shelf_bg_animation_setter.SetTweenType(gfx::Tween::EASE_OUT);
   shelf_bg_animation_setter.SetPreemptionStrategy(
       ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
-  shelf_bg_animation_setter.SetAnimationMetricsReporter(
-      animation_metrics_reporter_.get());
   animation_complete_callback_ = base::BindOnce(
       &HotseatTransitionAnimator::NotifyHotseatTransitionAnimationEnded,
       weak_ptr_factory_.GetWeakPtr(), old_state, new_state);

ash/shelf/hotseat_transition_animator.h

@@ -49,8 +49,6 @@ class HotseatTransitionAnimator : public TabletModeObserver,
   void OnTabletModeEnded() override;
 
  private:
-  class TransitionAnimationMetricsReporter;
-
   // Starts the animation between |old_state_| and |target_state_|.
   void DoAnimation(HotseatState old_state, HotseatState new_state);
 
@@ -81,10 +79,6 @@ class HotseatTransitionAnimator : public TabletModeObserver,
 
   base::ObserverList<Observer> observers_;
 
-  // Metric reporter for hotseat transitions.
-  const std::unique_ptr<TransitionAnimationMetricsReporter>
-      animation_metrics_reporter_;
-
   base::WeakPtrFactory<HotseatTransitionAnimator> weak_ptr_factory_{this};
 };