Adds UMA for screen rotation animation smoothness.

ash/rotator/screen_rotation_animator.cc

Index: ash/rotator/screen_rotation_animator.cc
diff --git a/ash/rotator/screen_rotation_animator.cc b/ash/rotator/screen_rotation_animator.cc
index c0dbe2058d6f7a4c33314ed1f07650cde2446195..cda85cb88eac97a8e7fabcf1354158b186f7f0e1 100644
--- a/ash/rotator/screen_rotation_animator.cc
+++ b/ash/rotator/screen_rotation_animator.cc
@@ -14,6 +14,7 @@
 #include "ash/shell.h"
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "ui/aura/window.h"
 #include "ui/compositor/layer.h"
@@ -47,6 +48,10 @@ const int kRotationDurationInMs = 250;
 const int kCounterClockWiseRotationFactor = 1;
 const int kClockWiseRotationFactor = -1;
 
+// The percentage histogram boundary.
+const int kPercentage_MIN = 1;
+const int kPercentage_MAX = 101;

[varkha, 2017/03/24 20:38:21]

Don't need those if you use UMA_HISTOGRAM_PERCENTAGE.

[wutao, 2017/03/24 21:48:24]

Will remove.

+
 // Aborts the active animations of the layer, and recurses upon its child
 // layers.
 void AbortAnimations(ui::Layer* layer) {
@@ -143,7 +148,7 @@ LayerCleanupObserver::~LayerCleanupObserver() {
 void LayerCleanupObserver::OnLayerAnimationEnded(
     ui::LayerAnimationSequence* sequence) {
   if (animator_)
-    animator_->OnLayerAnimationEnded();
+    animator_->ProcessAnimationQueue();
 
   delete this;
 }
@@ -151,7 +156,7 @@ void LayerCleanupObserver::OnLayerAnimationEnded(
 void LayerCleanupObserver::OnLayerAnimationAborted(
     ui::LayerAnimationSequence* sequence) {
   if (animator_)
-    animator_->OnLayerAnimationAborted();
+    animator_->ProcessAnimationQueue();
 
   delete this;
 }
@@ -177,13 +182,35 @@ struct ScreenRotationAnimator::ScreenRotationRequest {
   display::Display::RotationSource source;
 };
 
+class ScreenRotationAnimator::ScreenRotationAnimationMetricsReporter
+    : public ui::AnimationMetricsReporter {
+  void Report(int value) override {
+    base::LinearHistogram::FactoryGet(

[Mark P, 2017/03/24 20:32:41]

Maybe I haven't thought about this enough, but why can't you use the
UMA_HISTOGRAM_PERCENTAGE macro?

[varkha, 2017/03/24 20:38:21]

UMA_HISTOGRAM_PERCENTAGE("Ash.Rotation.AnimationSmoothness", value);
should indeed do the same thing.

[wutao, 2017/03/24 21:48:24]

Thanks.

[wutao, 2017/03/24 21:48:24]

I was confused by the use case of UMA_HISTOGRAM_PERCENTAGE and FactoryGet.
Changed to UMA_HISTOGRAM_PERCENTAGE.

+        "Ash.Rotation.AnimationSmoothness", kPercentage_MIN, kPercentage_MAX,
+        kPercentage_MAX + 1, base::HistogramBase::kUmaTargetedHistogramFlag)
+        ->Add(value);
+  }
+};
+
 ScreenRotationAnimator::ScreenRotationAnimator(int64_t display_id)
     : display_id_(display_id),
       is_rotating_(false),
+      metrics_reporter_(
+          base::MakeUnique<ScreenRotationAnimationMetricsReporter>()),
       disable_animation_timers_for_test_(false),
       weak_factory_(this) {}
 
-ScreenRotationAnimator::~ScreenRotationAnimator() {}
+ScreenRotationAnimator::~ScreenRotationAnimator() {
+  // To prevent a call to |LayerCleanupObserver::OnLayerAnimationAborted()| from
+  // calling a method on the |animator_|.
+  weak_factory_.InvalidateWeakPtrs();
+
+  // Explicitly reset the |old_layer_tree_owner_| and |metrics_reporter_| in
+  // order to make sure |metrics_reporter_| outlives the attached animation
+  // sequence.
+  old_layer_tree_owner_.reset();
+  metrics_reporter_.reset();
+}
 
 void ScreenRotationAnimator::AnimateRotation(
     std::unique_ptr<ScreenRotationRequest> rotation_request) {
@@ -278,6 +305,7 @@ void ScreenRotationAnimator::AnimateRotation(
   // control the animation.
   if (disable_animation_timers_for_test_)
     animator->set_disable_timer_for_test(true);
+  animation_sequence->SetAnimationMetricsReporter(metrics_reporter_.get());
   animator->StartAnimation(animation_sequence.release());
 
   rotation_request.reset();
@@ -313,15 +341,6 @@ void ScreenRotationAnimator::RemoveScreenRotationAnimatorObserver(
   screen_rotation_animator_observers_.RemoveObserver(observer);
 }
 
-void ScreenRotationAnimator::OnLayerAnimationEnded() {
-  ProcessAnimationQueue();
-}
-
-void ScreenRotationAnimator::OnLayerAnimationAborted() {
-  AbortAnimations(old_layer_tree_owner_->root());
-  ProcessAnimationQueue();
-}
-
 void ScreenRotationAnimator::ProcessAnimationQueue() {
   is_rotating_ = false;
   old_layer_tree_owner_.reset();