Scheduler: Add per task type duration metric split by use case: None, Loading and Input Handling.

Add RendererScheduler.TaskDurationPerTaskType.UseCase histogram to record time
we spend running tasks of different task types split per RendererScheduler's UseCase.

Change-Id: Icd53e095f5cbbddb5419207b2b5767aa2f09bf62
Reviewed-on: https://chromium-review.googlesource.com/968511Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: Farah Charab <farahcharab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#544200}

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

@@ -98,6 +98,12 @@ RendererMetricsHelper::RendererMetricsHelper(
           DURATION_PER_QUEUE_TYPE_METRIC_NAME ".HiddenMusic"),
       per_frame_status_duration_reporter_(DURATION_PER_FRAME_TYPE_METRIC_NAME),
       per_task_type_duration_reporter_(DURATION_PER_TASK_TYPE_METRIC_NAME),
+      no_use_case_per_task_type_duration_reporter_(
+          DURATION_PER_TASK_TYPE_METRIC_NAME ".UseCaseNone"),
+      loading_per_task_type_duration_reporter_(
+          DURATION_PER_TASK_TYPE_METRIC_NAME ".UseCaseLoading"),
+      input_handling_per_task_type_duration_reporter_(
+          DURATION_PER_TASK_TYPE_METRIC_NAME ".UseCaseInputHandling"),
       foreground_per_task_type_duration_reporter_(
           DURATION_PER_TASK_TYPE_METRIC_NAME ".Foreground"),
       background_per_task_type_duration_reporter_(
@@ -369,8 +375,17 @@ void RendererMetricsHelper::RecordTaskMetrics(
                               frame_status, FrameStatus::kCount);
   }
 
-  per_task_use_case_duration_reporter_.RecordTask(
-      renderer_scheduler_->main_thread_only().current_use_case, duration);
+  UseCase use_case = renderer_scheduler_->main_thread_only().current_use_case;
+  per_task_use_case_duration_reporter_.RecordTask(use_case, duration);
+  if (use_case == UseCase::kNone) {
+    no_use_case_per_task_type_duration_reporter_.RecordTask(task_type,
+                                                            duration);
+  } else if (use_case == UseCase::kLoading) {
+    loading_per_task_type_duration_reporter_.RecordTask(task_type, duration);
+  } else {
+    input_handling_per_task_type_duration_reporter_.RecordTask(task_type,
+                                                               duration);
+  }
 }
 
 void RendererMetricsHelper::RecordMainThreadTaskLoad(base::TimeTicks time,

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

@@ -121,6 +121,18 @@ class PLATFORM_EXPORT RendererMetricsHelper : public MetricsHelper {
       TaskDurationMetricReporter<TaskType>;
 
   TaskDurationPerTaskTypeMetricReporter per_task_type_duration_reporter_;
+
+  // The next three reporters are used to report the duration per task type
+  // split by renderer scheduler use case (check use_case.h for reference):
+  // None, Loading, and User Input (aggregation of multiple input-handling
+  // related use cases).
+  TaskDurationPerTaskTypeMetricReporter
+      no_use_case_per_task_type_duration_reporter_;
+  TaskDurationPerTaskTypeMetricReporter
+      loading_per_task_type_duration_reporter_;
+  TaskDurationPerTaskTypeMetricReporter
+      input_handling_per_task_type_duration_reporter_;
+
   TaskDurationPerTaskTypeMetricReporter
       foreground_per_task_type_duration_reporter_;
   TaskDurationPerTaskTypeMetricReporter

tools/metrics/histograms/histograms.xml

@@ -113370,6 +113370,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <affected-histogram name="RendererScheduler.TaskDurationPerQueueType2"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="RendererScheduler.TaskDurationPerTaskTypeSplit"
+    separator=".">
+  <suffix name="UseCaseNone"/>
+  <suffix name="UseCaseLoading"/>
+  <suffix name="UseCaseInputHandling"/>
+  <affected-histogram name="RendererScheduler.TaskDurationPerTaskType"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="RendererThreadType" separator=".">
   <suffix name="Main" label="Measurement taken on the main/render thread."/>
   <suffix name="Compositor"