scheduler: Disable expensive timers during main thread user input

components/scheduler/renderer/task_cost_estimator.h

+// Copyright 2015 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 COMPONENTS_SCHEDULER_RENDERER_TASK_COST_ESTIMATOR_H_
+#define COMPONENTS_SCHEDULER_RENDERER_TASK_COST_ESTIMATOR_H_
+
+#include "base/message_loop/message_loop.h"
+#include "base/time/time.h"
+#include "cc/base/rolling_time_delta_history.h"
+#include "components/scheduler/scheduler_export.h"
+
+namespace scheduler {
+
+// Estimates the cost of running tasks based on historical timing data.
+class SCHEDULER_EXPORT TaskCostEstimator
+    : public base::MessageLoop::TaskObserver {
+ public:
+  TaskCostEstimator(int sample_count, double estimation_percentile);
+  ~TaskCostEstimator() override;
+
+  base::TimeDelta expected_task_duration() const {
+    return expected_task_duration_;
+  }
+
+  // TaskObserver implementation:
+  void WillProcessTask(const base::PendingTask& pending_task) override;
+  void DidProcessTask(const base::PendingTask& pending_task) override;
+
+ protected:
+  // Virtual for testing.
+  virtual base::TimeTicks Now();
+
+ private:
+  cc::RollingTimeDeltaHistory rolling_time_delta_history_;
+  int outstanding_task_count_;
+  double estimation_percentile_;
+  base::TimeTicks task_start_time_;
+  base::TimeDelta expected_task_duration_;
+
+  DISALLOW_COPY_AND_ASSIGN(TaskCostEstimator);
+};
+
+}  // namespace scheduler
+
+#endif  // COMPONENTS_SCHEDULER_RENDERER_TASK_COST_ESTIMATOR_H_