[Android] Adding UMA for events in Background Task Scheduler

components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.java

Index: components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.java
diff --git a/components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.java b/components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.java
index e690273845cec8b60d884414c42f4836b2c5325b..bf85375d2d20769ff61118d1e017d923b3e949ae 100644
--- a/components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.java
+++ b/components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.java
@@ -77,6 +77,7 @@ public class BackgroundTaskScheduler {
     public boolean schedule(Context context, TaskInfo taskInfo) {
         ThreadUtils.assertOnUiThread();
         boolean success = mSchedulerDelegate.schedule(context, taskInfo);
+        BackgroundTaskSchedulerUma.getInstance().reportTaskScheduled(taskInfo.getTaskId(), success);
         if (success) {
             BackgroundTaskSchedulerPrefs.addScheduledTask(taskInfo);
         }
@@ -91,6 +92,7 @@ public class BackgroundTaskScheduler {
      */
     public void cancel(Context context, int taskId) {
         ThreadUtils.assertOnUiThread();
+        BackgroundTaskSchedulerUma.getInstance().reportTaskCanceled(taskId);
         BackgroundTaskSchedulerPrefs.removeScheduledTask(taskId);
         mSchedulerDelegate.cancel(context, taskId);
     }
@@ -105,14 +107,19 @@ public class BackgroundTaskScheduler {
     public void checkForOSUpgrade(Context context) {
         int oldSdkInt = BackgroundTaskSchedulerPrefs.getLastSdkVersion();
         int newSdkInt = Build.VERSION.SDK_INT;
-        // No OS upgrade detected.
-        if (oldSdkInt == newSdkInt) return;
 
-        // Save the current SDK version to preferences.
-        BackgroundTaskSchedulerPrefs.setLastSdkVersion(newSdkInt);
+        if (oldSdkInt != newSdkInt) {
+            // Save the current SDK version to preferences.
+            BackgroundTaskSchedulerPrefs.setLastSdkVersion(newSdkInt);
+        }
+
+        // No OS upgrade detected or OS upgrade does not change delegate.
+        if (oldSdkInt == newSdkInt || !osUpgradeChangesDelegateType(oldSdkInt, newSdkInt)) {
+            BackgroundTaskSchedulerUma.getInstance().flushStats();
+            return;
+        }
 
-        // Check for OS upgrades forcing delegate change or "just in case" rescheduling.
-        if (!osUpgradeChangesDelegateType(oldSdkInt, newSdkInt)) return;
+        BackgroundTaskSchedulerUma.getInstance().removeCachedStats();
 
         // Explicitly create and invoke old delegate type to cancel all scheduled tasks.
         // All preference entries are kept until reschedule call, which removes then then.