UMA stats for stylus usage

ash/common/metrics/pointer_metrics_recorder.h

Index: ash/common/metrics/pointer_metrics_recorder.h
diff --git a/ash/common/metrics/pointer_metrics_recorder.h b/ash/common/metrics/pointer_metrics_recorder.h
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index 0000000000000000000000000000000000000000..bf19e9098fcb41b9124a414c59cb69b89191a339
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+++ b/ash/common/metrics/pointer_metrics_recorder.h
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+// 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_COMMON_METRICS_POINTER_METRICS_RECORDER_H_
+#define UI_ASH_COMMON_METRICS_POINTER_METRICS_RECORDER_H_
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+#include "ui/views/pointer_watcher.h"
+
+namespace gfx {
+class Point;
+}
+
+namespace ui {
+class PointerEvent;
+}
+
+namespace ash {
+
+// A metrics recorder that records pointer related metrics.
+class ASH_EXPORT 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_COMMON_METRICS_POINTER_METRICS_RECORDER_H_