[scheduler] Add keep-active in background metrics.

Measure the amount of work done in background when keep-active signal is
present. This is to allow us to test the theory that we stopped stopping
timers in background after 5 minutes on Android due to widespread
keep-active signal.

R=panicker@chromium.org,rkaplow@chromium.org
BUG=823482

Change-Id: I653016d795a1903ea9d943e3c2b962ab9c1ba088
Reviewed-on: https://chromium-review.googlesource.com/973225Reviewed-by: Shubhie Panicker <panicker@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545126}

third_party/WebKit/Source/platform/scheduler/renderer/renderer_metrics_helper.h

@@ -83,37 +83,30 @@ class PLATFORM_EXPORT RendererMetricsHelper : public MetricsHelper {
   using TaskDurationPerQueueTypeMetricReporter =
       TaskDurationMetricReporter<MainThreadTaskQueue::QueueType>;
 
-  TaskDurationPerQueueTypeMetricReporter per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      foreground_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      foreground_first_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      foreground_second_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      foreground_third_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      foreground_after_third_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      background_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      background_first_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      background_second_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      background_third_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      background_fourth_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      background_fifth_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      background_after_fifth_minute_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      hidden_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      visible_per_queue_type_task_duration_reporter_;
-  TaskDurationPerQueueTypeMetricReporter
-      hidden_music_per_queue_type_task_duration_reporter_;
+  struct PerQueueTypeDurationReporters {
+    PerQueueTypeDurationReporters();
+
+    TaskDurationPerQueueTypeMetricReporter overall;
+    TaskDurationPerQueueTypeMetricReporter foreground;
+    TaskDurationPerQueueTypeMetricReporter foreground_first_minute;
+    TaskDurationPerQueueTypeMetricReporter foreground_second_minute;
+    TaskDurationPerQueueTypeMetricReporter foreground_third_minute;
+    TaskDurationPerQueueTypeMetricReporter foreground_after_third_minute;
+    TaskDurationPerQueueTypeMetricReporter background;
+    TaskDurationPerQueueTypeMetricReporter background_first_minute;
+    TaskDurationPerQueueTypeMetricReporter background_second_minute;
+    TaskDurationPerQueueTypeMetricReporter background_third_minute;
+    TaskDurationPerQueueTypeMetricReporter background_fourth_minute;
+    TaskDurationPerQueueTypeMetricReporter background_fifth_minute;
+    TaskDurationPerQueueTypeMetricReporter background_after_fifth_minute;
+    TaskDurationPerQueueTypeMetricReporter
+        background_keep_active_after_fifth_minute;
+    TaskDurationPerQueueTypeMetricReporter hidden;
+    TaskDurationPerQueueTypeMetricReporter visible;
+    TaskDurationPerQueueTypeMetricReporter hidden_music;
+  };
+
+  PerQueueTypeDurationReporters per_queue_type_reporters_;
 
   TaskDurationMetricReporter<FrameStatus> per_frame_status_duration_reporter_;
 

tools/metrics/histograms/histograms.xml

@@ -113588,6 +113588,10 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
       label="Time spent in tasks of a particular type starting from the sixth
              minute after backgrounding the renderer. The renderer is
              expected to be mostly idle during this period."/>
+  <suffix name="Background.KeepAlive.AfterFifthMinute"
+      label="Time spent in tasks of a particular type starting from the sixth
+             minute after backgrounding the renderer when keep-alive signal
+             is present."/>
   <suffix name="Foreground"
       label="Time spent in tasks of a particular type when the renderer is in
              the foreground. Please note that individual tabs in this