[Android] Adding UMA for events in Background Task Scheduler

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index fde40f26e83c1fb6e0e6d8f46a4ca389d4d8b413..367e42f5ef26dbb76c5dc06905980d4b81191192 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4698,6 +4698,45 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="BackgroundTaskScheduler.TaskCanceled" enum="BackgroundTaskId">

[Alexei Svitkine (slow), 2017/06/01 17:03:34]

Nit: Suggest prefixing these with "Android." since the BackgroundTaskScheduler
is an Android thing.

So Android.BackgroundTaskSchedular.TaskCanceled

+  <owner>fgorski@chromium.org</owner>
+  <owner>nyquist@chromium.org</owner>
+  <summary>Records that a specific background task has been canceled.</summary>
+</histogram>
+
+<histogram name="BackgroundTaskScheduler.TaskScheduled.Failure"
+    enum="BackgroundTaskId">
+  <owner>fgorski@chromium.org</owner>
+  <owner>nyquist@chromium.org</owner>
+  <summary>
+    Records that a specific background task has failed to be scheduled.
+  </summary>
+</histogram>
+
+<histogram name="BackgroundTaskScheduler.TaskScheduled.Success"
+    enum="BackgroundTaskId">
+  <owner>fgorski@chromium.org</owner>
+  <owner>nyquist@chromium.org</owner>
+  <summary>
+    Records that a specific background task has been successfully scheduled.
+  </summary>
+</histogram>
+
+<histogram name="BackgroundTaskScheduler.TaskStarted" enum="BackgroundTaskId">
+  <owner>fgorski@chromium.org</owner>
+  <owner>nyquist@chromium.org</owner>
+  <summary>Records that a specific background task has been started.</summary>
+</histogram>
+
+<histogram name="BackgroundTaskScheduler.TaskStopped" enum="BackgroundTaskId">
+  <owner>fgorski@chromium.org</owner>
+  <owner>nyquist@chromium.org</owner>
+  <summary>
+    Records that a specific background task has been stopped by Background Task
+    Scheduler before it was able to complete itself.
+  </summary>
+</histogram>
+
 <histogram name="BatteryStatus.NumberBatteriesLinux"
     enum="BatteryStatusNumberBatteries">
   <owner>timvolodine@chromium.org</owner>