[settings logging] Add unit tests for the logging functions.

Bug: 1014839
Change-Id: Ie568d00cd2a40b104ea204b6e73e6a73f8cb5e3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2029389Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Tony Yeoman <tby@chromium.org>
Commit-Queue: Rachel Wong <wrong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738742}

ash/BUILD.gn

@@ -1874,6 +1874,7 @@ test("ash_unittests") {
     "system/ime/ime_feature_pod_controller_unittest.cc",
     "system/ime_menu/ime_menu_tray_unittest.cc",
     "system/locale/locale_feature_pod_controller_unittest.cc",
+    "system/machine_learning/user_settings_event_logger_unittest.cc",
     "system/message_center/arc/arc_notification_content_view_unittest.cc",
     "system/message_center/arc/arc_notification_manager_unittest.cc",
     "system/message_center/arc/arc_notification_view_unittest.cc",
@@ -2052,6 +2053,7 @@ test("ash_unittests") {
     "//ash/public/cpp/vector_icons",
     "//ash/resources/vector_icons",
     "//ash/strings",
+    "//ash/system/machine_learning:user_settings_event_proto",
     "//ash/system/message_center/arc",
     "//ash/system/message_center/arc:test_support",
     "//base",
@@ -2088,6 +2090,7 @@ test("ash_unittests") {
     "//components/prefs:test_support",
     "//components/quirks",
     "//components/sync_preferences:test_support",
+    "//components/ukm:test_support",
     "//components/user_manager",
     "//components/user_manager:test_support",
     "//device/bluetooth",
@@ -2100,6 +2103,7 @@ test("ash_unittests") {
     "//services/device/public/cpp/bluetooth",
     "//services/media_session/public/cpp/test:test_support",
     "//services/media_session/public/mojom",
+    "//services/metrics/public/cpp:ukm_builders",
     "//skia",
     "//testing/gmock",
     "//testing/gtest",

ash/system/machine_learning/DEPS

 include_rules = [
+  "+components/ukm/test_ukm_recorder.h",
   "+services/metrics/public/cpp",
 ]

ash/system/machine_learning/user_settings_event_logger.cc

@@ -55,7 +55,6 @@ UserSettingsEventLogger::~UserSettingsEventLogger() {
   chromeos::CrasAudioHandler::Get()->RemoveAudioObserver(this);
 }
 
-// TODO(crbug/1014839): Write unit tests for the LogUkmEvent methods.
 void UserSettingsEventLogger::LogNetworkUkmEvent(
     const NetworkStateProperties& network) {
   UserSettingsEvent settings_event;

ash/system/machine_learning/user_settings_event_logger.h

@@ -17,8 +17,8 @@ namespace ash {
 namespace ml {
 
 // This class handles logging for settings changes that are initiated by the
-// user from the quick settings tray.
-class UserSettingsEventLogger
+// user from the quick settings tray. Exported for tests.
+class ASH_EXPORT UserSettingsEventLogger
     : public ShellObserver,
       public chromeos::CrasAudioHandler::AudioObserver {
  public: