blink scheduler: Record UMA for load after fifth minute in background.

We intend to use this new histogram to trigger slow reports for users
where load of a background tab is high.

Bug: 848691
Change-Id: I7dd524f77a8be3f86e0678f0a4c1711d6b077779
Reviewed-on: https://chromium-review.googlesource.com/1082393Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563629}

third_party/blink/renderer/platform/scheduler/main_thread/main_thread_metrics_helper.cc

@@ -445,9 +445,10 @@ void MainThreadMetricsHelper::RecordForegroundMainThreadTaskLoad(
       UMA_HISTOGRAM_PERCENTAGE(MAIN_THREAD_LOAD_METRIC_NAME ".Foreground",
                                load_percentage);
 
-      if (time - main_thread_scheduler_->main_thread_only()
-                     .background_status_changed_at >
-          base::TimeDelta::FromMinutes(1)) {
+      base::TimeDelta time_since_foregrounded =
+          time - main_thread_scheduler_->main_thread_only()
+                     .background_status_changed_at;
+      if (time_since_foregrounded > base::TimeDelta::FromMinutes(1)) {
         UMA_HISTOGRAM_PERCENTAGE(MAIN_THREAD_LOAD_METRIC_NAME
                                  ".Foreground.AfterFirstMinute",
                                  load_percentage);
@@ -476,13 +477,19 @@ void MainThreadMetricsHelper::RecordBackgroundMainThreadTaskLoad(
       UMA_HISTOGRAM_PERCENTAGE(MAIN_THREAD_LOAD_METRIC_NAME ".Background",
                                load_percentage);
 
-      if (time - main_thread_scheduler_->main_thread_only()
-                     .background_status_changed_at >
-          base::TimeDelta::FromMinutes(1)) {
+      base::TimeDelta time_since_backgrounded =
+          time - main_thread_scheduler_->main_thread_only()
+                     .background_status_changed_at;
+      if (time_since_backgrounded > base::TimeDelta::FromMinutes(1)) {
         UMA_HISTOGRAM_PERCENTAGE(MAIN_THREAD_LOAD_METRIC_NAME
                                  ".Background.AfterFirstMinute",
                                  load_percentage);
       }
+      if (time_since_backgrounded > base::TimeDelta::FromMinutes(5)) {
+        UMA_HISTOGRAM_PERCENTAGE(MAIN_THREAD_LOAD_METRIC_NAME
+                                 ".Background.AfterFifthMinute",
+                                 load_percentage);
+      }
       break;
   }
 

tools/metrics/histograms/histograms.xml

@@ -119979,6 +119979,9 @@ uploading your change for review.
   <suffix name="Background"
       label="Main thread load when the renderer is backgrounded. This does
              not include extension renderers."/>
+  <suffix name="Background.AfterFifthMinute"
+      label="Main thread load when the renderer is backgrounded for longer
+             than five minutes. This does not include extension renderers."/>
   <suffix name="Background.AfterFirstMinute"
       label="Main thread load when the renderer is backgrounded for longer
              than one minute. Most of loading tasks are expected to complete