ash: Use ThroughputTracker for homescreen smoothness

Bug: 1021774
Change-Id: I1fa60f4f920e2cade3b2fd9249f85cf049c8564b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2268085Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#782651}

ash/home_screen/home_screen_controller.cc

@@ -12,7 +12,7 @@
 #include "ash/home_screen/home_screen_delegate.h"
 #include "ash/home_screen/window_scale_animation.h"
 #include "ash/public/cpp/ash_features.h"
-#include "ash/public/cpp/fps_counter.h"
+#include "ash/public/cpp/metrics_util.h"
 #include "ash/public/cpp/shell_window_ids.h"
 #include "ash/public/cpp/window_properties.h"
 #include "ash/scoped_animation_disabler.h"
@@ -28,11 +28,13 @@
 #include "ash/wm/window_transient_descendant_iterator.h"
 #include "ash/wm/window_util.h"
 #include "base/barrier_closure.h"
+#include "base/bind.h"
 #include "base/check.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
 #include "ui/aura/window.h"
 #include "ui/compositor/layer_animation_observer.h"
+#include "ui/compositor/throughput_tracker.h"
 #include "ui/display/manager/display_manager.h"
 #include "ui/wm/core/window_animations.h"
 
@@ -302,16 +304,18 @@ void HomeScreenController::StartTrackingAnimationSmoothness(
     int64_t display_id) {
   auto* root_window = Shell::GetRootWindowForDisplayId(display_id);
   auto* compositor = root_window->layer()->GetCompositor();
-  fps_counter_ = std::make_unique<FpsCounter>(compositor);
+  smoothness_tracker_ = compositor->RequestNewThroughputTracker();
+  smoothness_tracker_->Start(
+      metrics_util::ForSmoothness(base::BindRepeating([](int smoothness) {
+        UMA_HISTOGRAM_PERCENTAGE(kHomescreenAnimationHistogram, smoothness);
+      })));
 }
 
 void HomeScreenController::RecordAnimationSmoothness() {
-  if (!fps_counter_)
+  if (!smoothness_tracker_)
     return;
-  int smoothness = fps_counter_->ComputeSmoothness();
-  if (smoothness >= 0)
-    UMA_HISTOGRAM_PERCENTAGE(kHomescreenAnimationHistogram, smoothness);
-  fps_counter_.reset();
+  smoothness_tracker_->Stop();
+  smoothness_tracker_.reset();
 }
 
 void HomeScreenController::OnAppListViewShown() {

ash/home_screen/home_screen_controller.h

@@ -19,9 +19,12 @@
 #include "base/optional.h"
 #include "base/scoped_observer.h"
 
+namespace ui {
+class ThroughputTracker;
+}
+
 namespace ash {
 
-class FpsCounter;
 class HomeLauncherGestureHandler;
 class HomeScreenDelegate;
 
@@ -56,7 +59,7 @@ class ASH_EXPORT HomeScreenController : public OverviewObserver,
   // True if home screen is visible.
   bool IsHomeScreenVisible() const;
 
-  // Responsible to starting or stopping |fps_counter_|.
+  // Responsible to starting or stopping |smoothness_tracker_|.
   void StartTrackingAnimationSmoothness(int64_t display_id);
   void RecordAnimationSmoothness();
 
@@ -134,7 +137,7 @@ class ASH_EXPORT HomeScreenController : public OverviewObserver,
 
   // Responsible for recording smoothness related UMA stats for homescreen
   // animations.
-  std::unique_ptr<FpsCounter> fps_counter_;
+  base::Optional<ui::ThroughputTracker> smoothness_tracker_;
 
   ScopedObserver<SplitViewController, SplitViewObserver> split_view_observer_{
       this};

ash/home_screen/home_screen_controller_unittest.cc

@@ -152,6 +152,13 @@ TEST_P(HomeScreenControllerTest, DraggingHistograms) {
   // should have a animation smoothness histogram recorded.
   if (drag_enabled) {
     ShellTestApi().WaitForWindowFinishAnimating(window.get());
+
+    // Wait for one more frame presented for the metrics to get recorded.
+    // ignore_result() and timeout is because the frame could already be
+    // presented.
+    ignore_result(ui::WaitForNextFrameToBePresented(
+        compositor, base::TimeDelta::FromMilliseconds(500)));
+
     tester.ExpectTotalCount(kHomescreenAnimationHistogram, 1);
   }
 }