Report expected task queueing time via UMA

components/scheduler/base/task_time_tracker.h

Index: components/scheduler/base/task_time_tracker.h
diff --git a/components/scheduler/base/task_time_tracker.h b/components/scheduler/base/task_time_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..80d80072e7ac53e6758cb7b468df741308dae7f2
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+++ b/components/scheduler/base/task_time_tracker.h
@@ -0,0 +1,51 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_RENDERER_SCHEDULER_BASE_TASK_TIME_TRACKER_H_
+#define CONTENT_RENDERER_SCHEDULER_BASE_TASK_TIME_TRACKER_H_
+
+#include <memory>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/time/default_tick_clock.h"
+#include "base/time/time.h"
+#include "components/scheduler/base/queueing_time_estimator.h"
+#include "components/scheduler/scheduler_export.h"
+
+namespace base {
+class TickClock;
+}
+
+namespace scheduler {
+
+class SCHEDULER_EXPORT TaskTimeTracker : public QueueingTimeEstimator::Client {
+ public:
+  class TaskTimeObserver {
+   public:
+    virtual void OnQueueingTimeForWindowEstimated(
+        base::TimeDelta queueing_time) = 0;
+    virtual ~TaskTimeObserver() {}
+  };
+
+  TaskTimeTracker();
+  ~TaskTimeTracker() override;
+
+  void ReportTaskTime(base::TimeTicks startTime, base::TimeTicks endTime);
+  void SetObserver(TaskTimeObserver*);
+
+ protected:
+  // QueueingTimeEstimator::Client implementation:
+  void OnQueueingTimeForWindowEstimated(base::TimeDelta queueing_time) override;
+
+ private:
+  TaskTimeObserver* task_time_observer_;  // Not Owned
+  QueueingTimeEstimator queueing_time_estimator_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskTimeTracker);
+}; // scheduler
+
+#endif // CONTENT_RENDERER_SCHEDULER_BASE_TASK_TIME_TRACKER_H_
+
+}