UMA stats for stylus usage

chrome/browser/ui/ash/metrics/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 CHROME_BROWSER_UI_ASH_METRICS_STYLUS_METRICS_RECORDER_H_
+#define CHROME_BROWSER_UI_ASH_METRICS_STYLUS_METRICS_RECORDER_H_
+
+#include "base/macros.h"
+#include "ui/aura/client/aura_constants.h"

[sky, 2016/09/13 00:03:26]

Can this include be moved to .cc?

[xiaoyinh(OOO Sep 11-29), 2016/09/16 18:41:16]

I moved the window property key out of aura::client, so this include is removed.
Thanks!

+#include "ui/views/pointer_watcher.h"
+
+namespace gfx {
+class Point;
+}
+
+namespace ui {
+class PointerEvent;
+}
+
+namespace chromeos {
+
+// Form factor of the down event. This enum is used to back an UMA histogram
+// and should be treated as append-only.
+enum DownEventFormFactor {

[sky, 2016/09/13 00:03:26]

Please use enum class.

[xiaoyinh(OOO Sep 11-29), 2016/09/16 18:41:16]

Thanks! I've made StylusWindowType as enum class. Other 3 are used in UMA
HISTGRAM. And UMA seems to only accept int as samples.

../chrome/browser/ui/ash/metrics/stylus_metrics_recorder.cc:147:68: error:
cannot initialize a parameter of type 'Sample' (aka 'int') with an lvalue of
type 'chromeos::DownEventDestination'
UMA_HISTOGRAM_ENUMERATION("Event.DownEventCount.PerDestination", dest,

+  DOWN_EVENT_FORMFACTOR_CLAMSHELL = 0,
+  DOWN_EVENT_FORMFACTOR_TOUCHVIEW,
+  DOWN_EVENT_FORMFACTOR_COUNT
+};
+
+// Input type of the down event. This enum is used to back an UMA
+// histogram and should be treated as append-only.
+enum DownEventSource {

[sky, 2016/09/13 00:03:26]

Move enums that are only used in the .cc into the .cc.

[xiaoyinh(OOO Sep 11-29), 2016/09/16 18:41:16]

Done.

+  DOWN_EVENT_SOURCE_UNKNOWN = 0,
+  DOWN_EVENT_SOURCE_MOUSE,
+  DOWN_EVENT_SOURCE_STYLUS,
+  DOWN_EVENT_SOURCE_TOUCH,
+  DOWN_EVENT_SOURCE_COUNT
+};
+
+// Destination of the down event. This enum is used to back
+// an UMA histogram and should be treated as append-only.
+enum DownEventDestination {
+  DOWN_EVENT_DESTINATION_OTHERS = 0,
+  DOWN_EVENT_DESTINATION_SYSTEM_UI,
+  DOWN_EVENT_DESTINATION_WEBSITE,
+  DOWN_EVENT_DESTINATION_ARC_APP,
+  DOWN_EVENT_DESTINATION_NOTE_TAKING_APP,
+  DOWN_EVENT_DESTINATION_COUNT
+};
+
+enum StylusWindowType {

[xiyuan, 2016/09/12 20:15:47]

Are those enums used elsewhere? If not, let's move them into cc file.

[xiaoyinh(OOO Sep 11-29), 2016/09/16 18:41:16]

Yes, they are being used when set the window property in 
chrome_native_app_window_views_aura_ash.cc and
browser_frame.cc

+  WINDOW_TYPE_OTHERS = 0,
+  WINDOW_TYPE_APP,
+  WINDOW_TYPE_BROWSER_WINDOW
+};
+
+// An metrics recorder that record stylus related metrics.
+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;
+
+  void RecordUMA(ui::EventPointerType type, views::Widget* target);
+
+  bool IsEventOnShelf(views::Widget* target);
+
+  DownEventDestination GetDownEventDestination(views::Widget* target);

[xiyuan, 2016/09/12 20:15:47]

RecordUMA, IsEventOnShelf and GetDownEventDestination are impl details and can
all be moved into an anonymous namespace in cc file.

[xiaoyinh(OOO Sep 11-29), 2016/09/16 18:41:16]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(StylusMetricsRecorder);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_UI_ASH_METRICS_STYLUS_METRICS_RECORDER_H_