UMA stats for stylus usage

ash/metrics/user_metrics_recorder.h

 // Copyright 2013 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_USER_METRICS_RECORDER_H_
 #define ASH_METRICS_USER_METRICS_RECORDER_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "ash/common/metrics/user_metrics_action.h"
 #include "ash/metrics/task_switch_metrics_recorder.h"
 #include "base/macros.h"
 #include "base/timer/timer.h"
 
 namespace ash {
 
 class DesktopTaskSwitchMetricRecorder;
 
+#if defined(OS_CHROMEOS)
+class PointerMetricsRecorder;
+#endif
+
 namespace test {
 class UserMetricsRecorderTestAPI;
 }
 
 // User Metrics Recorder provides a repeating callback (RecordPeriodicMetrics)
 // on a timer to allow recording of state data over time to the UMA records.
 // Any additional states (in ash) that require monitoring can be added to
 // this class. As well calls to record on action metrics
 // (RecordUserMetricsAction) are passed through the UserMetricsRecorder.
 class ASH_EXPORT UserMetricsRecorder {
@@ skipping 41 matching lines @@
   // The periodic timer that triggers metrics to be recorded.
   base::RepeatingTimer timer_;
 
   TaskSwitchMetricsRecorder task_switch_metrics_recorder_;
 
   // Metric recorder to track how often task windows are activated by mouse
   // clicks or touchscreen taps.
   std::unique_ptr<DesktopTaskSwitchMetricRecorder>
       desktop_task_switch_metric_recorder_;
 
+#if defined(OS_CHROMEOS)
+  // Metric recorder to track pointer down event.

[Daniel Erat, 2016/09/27 19:15:10]

nit: s/event/events/

[xiaoyinh(OOO Sep 11-29), 2016/09/29 20:37:43]

Done.

+  std::unique_ptr<PointerMetricsRecorder> pointer_metrics_recorder_;
+#endif
+
   DISALLOW_COPY_AND_ASSIGN(UserMetricsRecorder);
 };
 
 }  // namespace ash
 
 #endif  // ASH_METRICS_USER_METRICS_RECORDER_H_