[Android] Adding UMA for events in Background Task Scheduler

components/background_task_scheduler/BUILD.gn

Index: components/background_task_scheduler/BUILD.gn
diff --git a/components/background_task_scheduler/BUILD.gn b/components/background_task_scheduler/BUILD.gn
index e23f4837d71c066b466273c81ee88650a6650e0a..f77a15cc24451c8d74d208c5483a557b5e19665a 100644
--- a/components/background_task_scheduler/BUILD.gn
+++ b/components/background_task_scheduler/BUILD.gn
@@ -31,6 +31,7 @@ if (is_android) {
       "android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerGcmNetworkManager.java",
       "android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerJobService.java",
       "android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerPrefs.java",
+      "android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerUma.java",
       "android/java/src/org/chromium/components/background_task_scheduler/BundleToPersistableBundleConverter.java",
       "android/java/src/org/chromium/components/background_task_scheduler/TaskIds.java",
       "android/java/src/org/chromium/components/background_task_scheduler/TaskInfo.java",
@@ -68,6 +69,7 @@ if (is_android) {
       "android/junit/src/org/chromium/components/background_task_scheduler/BackgroundTaskGcmTaskServiceTest.java",
       "android/junit/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerPrefsTest.java",
       "android/junit/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerTest.java",
+      "android/junit/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerUmaTest.java",
       "android/junit/src/org/chromium/components/background_task_scheduler/ShadowGcmNetworkManager.java",
       "android/junit/src/org/chromium/components/background_task_scheduler/TestBackgroundTask.java",
     ]