Add Night Light UMA Histograms

Add two histograms to track in which range the color temperature is
mostly selected, and the type of the schedule.

BUG=740759

Change-Id: I978a02bcfe84bf770a3db93a0727e90b91ec36fd
Reviewed-on: https://chromium-review.googlesource.com/569002
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486603}

ash/public/interfaces/night_light_controller.mojom

@@ -19,6 +19,8 @@ struct SimpleGeoposition {
 
 // Used by a client (e.g. Chrome) to provide the current user's geoposition.
 interface NightLightController {
+  // These values are written to logs. New enum values can be added, but
+  // existing enums must never be renumbered or deleted and reused.
   enum ScheduleType {
     // Automatic toggling of NightLight is turned off.
     kNone = 0,
@@ -30,6 +32,9 @@ interface NightLightController {
     // Toggled automatically based on the custom set start and end times
     // selected by the user from the system settings.
     kCustom = 2,
+
+    // Must be the last item, used for UMA histograms.
+    kLast = kCustom,
   };
 
   // Sets the client that will be notified of changes in the Night Light

ash/system/night_light/night_light_controller.cc

@@ -4,11 +4,14 @@
 
 #include "ash/system/night_light/night_light_controller.h"
 
+#include <cmath>
+
 #include "ash/ash_switches.h"
 #include "ash/public/cpp/ash_pref_names.h"
 #include "ash/session/session_controller.h"
 #include "ash/shell.h"
 #include "base/command_line.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
@@ -78,6 +81,17 @@ class NightLightControllerDelegateImpl : public NightLightController::Delegate {
   DISALLOW_COPY_AND_ASSIGN(NightLightControllerDelegateImpl);
 };
 
+// Returns the color temperature range bucket in which |temperature| resides.
+// The range buckets are:
+// 0 => Range [0 : 20) (least warm).
+// 1 => Range [20 : 40).
+// 2 => Range [40 : 60).
+// 3 => Range [60 : 80).
+// 4 => Range [80 : 100) (most warm).
+int GetTemperatureRange(float temperature) {
+  return std::floor(5 * temperature);
+}
+
 // Applies the given |layer_temperature| to all the layers of the root windows
 // with the given |animation_duration|.
 // |layer_temperature| is the ui::Layer floating-point value in the range of
@@ -94,6 +108,10 @@ void ApplyColorTemperatureToLayers(float layer_temperature,
 
     layer->SetLayerTemperature(layer_temperature);
   }
+
+  UMA_HISTOGRAM_EXACT_LINEAR(
+      "Ash.NightLight.Temperature", GetTemperatureRange(layer_temperature),
+      5 /* number of buckets defined in GetTemperatureRange() */);
 }
 
 }  // namespace
@@ -337,6 +355,10 @@ void NightLightController::OnScheduleTypePrefChanged() {
   DCHECK(active_user_pref_service_);
   NotifyClientWithScheduleChange();
   Refresh(true /* did_schedule_change */);
+
+  // TODO(https://crbug.com/742517).
+  UMA_HISTOGRAM_ENUMERATION("Ash.NightLight.ScheduleType", GetScheduleType(),
+                            static_cast<int>(ScheduleType::kLast) + 1);
 }
 
 void NightLightController::OnCustomSchedulePrefsChanged() {

tools/metrics/histograms/enums.xml

@@ -1292,6 +1292,24 @@ uploading your change for review.  These are checked by presubmit scripts.
   <int value="5" label="INSUFFICIENT_RESOURCES"/>
 </enum>
 
+<enum name="AshNightLightScheduleType">
+  <summary>Defines the possible Night Light schedule types</summary>
+  <int value="0" label="None"/>
+  <int value="1" label="Sunset to Sunrise"/>
+  <int value="2" label="Custom Schedule"/>
+</enum>
+
+<enum name="AshNightLightTemperatureRanges">
+  <summary>
+    Defines the ranges in which the value of the color temperature may reside
+  </summary>
+  <int value="0" label="[0 to 20) (coldest)"/>
+  <int value="1" label="[20 to 40)"/>
+  <int value="2" label="[40 to 60)"/>
+  <int value="3" label="[60 to 80)"/>
+  <int value="4" label="[80 to 100) (warmest)"/>
+</enum>
+
 <enum name="AsyncDNSConfigParsePosix">
   <int value="0" label="OK"/>
   <int value="1" label="RES_INIT_FAILED"/>

tools/metrics/histograms/histograms.xml

@@ -2254,6 +2254,24 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Ash.NightLight.ScheduleType" enum="AshNightLightScheduleType">
+  <owner>afakhry@chromium.org</owner>
+  <summary>
+    The selected Night Light schedule type. Emitted when the user changes the
+    Night Light schedule type from the Display System Settings.
+  </summary>
+</histogram>
+
+<histogram name="Ash.NightLight.Temperature"
+    enum="AshNightLightTemperatureRanges">
+  <owner>afakhry@chromium.org</owner>
+  <summary>
+    The ranges in which the selected values of the Night Light color temperature
+    reside. Emitted when the user drags the Night Light color temperature slider
+    to change its value from the Display System Settings.
+  </summary>
+</histogram>
+
 <histogram name="Ash.NumberOfVisibleWindowsInPrimaryDisplay" units="Windows">
   <owner>tdanderson@google.com</owner>
   <owner>bruthig@google.com</owner>