UMA stats for stylus usage

ash/metrics/pointer_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 UI_ASH_METRICS_POINTER_METRICS_RECORDER_H_
+#define UI_ASH_METRICS_POINTER_METRICS_RECORDER_H_
+
+#include "base/macros.h"
+#include "ui/views/pointer_watcher.h"
+
+namespace gfx {
+class Point;
+}
+
+namespace ui {
+class PointerEvent;
+}
+
+namespace ash {

[sky, 2016/09/27 22:08:59]

Please move this class to ash/common/metrics. Add a getter to WmWindow for the
AppType that uses the property you added. Implement it for WmWindowAura and
leave TODOs for WmWindowMus.

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

Done. Also added SetAppType() in WmWindow so that
	ash/metrics/pointer_metrics_recorder_unittest.cc could use for testing.

+
+// A metrics recorder that records pointer related metrics.
+class PointerMetricsRecorder : public views::PointerWatcher {
+ public:
+  PointerMetricsRecorder();
+  ~PointerMetricsRecorder() override;
+
+  // views::PointerWatcher:
+  void OnPointerEventObserved(const ui::PointerEvent& event,
+                              const gfx::Point& location_in_screen,
+                              views::Widget* target) override;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PointerMetricsRecorder);
+};
+
+}  // namespace ash
+
+#endif  // UI_ASH_METRICS_POINTER_METRICS_RECORDER_H_