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// 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 ASH_METRICS_TASK_SWITCH_TIME_TRACKER_H_
#define ASH_METRICS_TASK_SWITCH_TIME_TRACKER_H_
#include <string>
#include "ash/ash_export.h"
#include "base/macros.h"
#include "base/memory/scoped_ptr.h"
#include "base/time/time.h"
namespace base {
class HistogramBase;
class TickClock;
}
namespace ash {
namespace test {
class TaskSwitchTimeTrackerTestAPI;
} // namespace test
// Tracks time deltas between task switches and records them in a histogram.
class ASH_EXPORT TaskSwitchTimeTracker {
public:
// Create a TaskSwitchTimeTracker that will record data to the histogram with
// the given |histogram_name|.
explicit TaskSwitchTimeTracker(const std::string& histogram_name);
~TaskSwitchTimeTracker();
// Notifies |this| that a task switch has occurred. A histogram data point
// will be recorded for all calls but the first.
void OnTaskSwitch();
private:
friend class test::TaskSwitchTimeTrackerTestAPI;
// Private constructor that the test::TaskSwitchTimeTrackerTestAPI can use to
// inject a custom |tick_clock|.
TaskSwitchTimeTracker(const std::string& histogram_name,
scoped_ptr<base::TickClock> tick_clock);
// Returns true if |last_action_time_| has a valid value.
bool HasLastActionTime() const;
// Sets the |last_action_time_| to |tick_clock_|'s current value and returns
// the previous value for |last_action_time_|.
base::TimeTicks SetLastActionTime();
// Records a data point in the histogram.
void RecordTimeDelta();
// Lazily obtains and sets the |histogram_|.
base::HistogramBase* GetHistogram();
// The histogram name to record data to.
std::string histogram_name_;
// The histogram to log data to. Set via GetHistogram() using lazy load.
base::HistogramBase* histogram_ = nullptr;
// Tracks the last time OnTaskSwitch() was called. A value of
// base::TimeTicks() should be interpreted as not set.
base::TimeTicks last_action_time_ = base::TimeTicks();
// The clock used to determine the |last_action_time_|.
scoped_ptr<base::TickClock> tick_clock_;
DISALLOW_COPY_AND_ASSIGN(TaskSwitchTimeTracker);
};
} // namespace ash
#endif // ASH_METRICS_TASK_SWITCH_TIME_TRACKE_H_
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