UMA stats for stylus usage

chrome/browser/ui/ash/metrics/stylus_metrics_recorder_chromeos.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 CHROME_BROWSER_UI_ASH_METRICS_STYLUS_METRICS_RECORDER_CHROMEOS_H_
+#define CHROME_BROWSER_UI_ASH_METRICS_STYLUS_METRICS_RECORDER_CHROMEOS_H_
+
+#include "base/macros.h"
+#include "ui/aura/window.h"
+#include "ui/views/pointer_watcher.h"
+
+namespace gfx {
+class Point;
+}
+
+namespace ui {
+class PointerEvent;
+}
+
+namespace chromeos {
+
+enum class StylusWindowType {
+  WINDOW_TYPE_OTHERS = 0,

[sky, 2016/09/16 23:20:16]

StylusWindowType::WINDOW_TYPE is a bit redundant, StylusWindowType::OTHER and
StylusWindowType::APP is more succinct.

[xiaoyinh(OOO Sep 11-29), 2016/09/19 21:19:53]

Done.

+  WINDOW_TYPE_APP,
+  WINDOW_TYPE_BROWSER_WINDOW,
+};
+
+// A property key to store the type of window that will be used to record stylus
+// metrics.
+extern const aura::WindowProperty<StylusWindowType>* const
+    kStylusWindowTypeBucket;
+
+// An metrics recorder that record stylus related metrics.

[sky, 2016/09/16 23:20:16]

An->A
record->records

[xiaoyinh(OOO Sep 11-29), 2016/09/19 21:19:53]

Thanks. Changed.

+class StylusMetricsRecorder : public views::PointerWatcher {
+ public:
+  StylusMetricsRecorder();
+  ~StylusMetricsRecorder() override;
+
+ private:
+  // views::PointerWatcher:
+  void OnPointerEventObserved(const ui::PointerEvent& event,
+                              const gfx::Point& location_in_screen,
+                              views::Widget* target) override;
+
+  DISALLOW_COPY_AND_ASSIGN(StylusMetricsRecorder);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_UI_ASH_METRICS_STYLUS_METRICS_RECORDER_CHROMEOS_H_