add stylus metrics

ash/wm/stylus_metrics_recorder.h

+// 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 ASH_WM_STYLUS_METRICS_RECORDER_H_
+#define ASH_WM_STYLUS_METRICS_RECORDER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "ui/events/event_handler.h"
+
+namespace ash {
+
+// An event recorder that record stylus related metrics.
+class StylusMetricsRecorder : public ui::EventHandler {
+ public:
+  StylusMetricsRecorder();
+  ~StylusMetricsRecorder() override;
+
+  // ui::EventHandler:

[jdufault, 2016/08/24 00:24:37]

Make override implementation private

[xiaoyinh(OOO Sep 11-29), 2016/08/24 16:51:51]

Done.

+  void OnMouseEvent(ui::MouseEvent* event) override;
+  void OnTouchEvent(ui::TouchEvent* event) override;
+
+ private:
+  void RecordUMA(ui::EventPointerType type);
+
+  DISALLOW_COPY_AND_ASSIGN(StylusMetricsRecorder);
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_STYLUS_METRICS_RECORDER_H_