UMA stats for stylus usage

ash/shared/app_types.h

Index: ash/shared/app_types.h
diff --git a/ash/shared/app_types.h b/ash/shared/app_types.h
new file mode 100644
index 0000000000000000000000000000000000000000..7741ce780be5118fc478e0108660fccaee25a018
--- /dev/null
+++ b/ash/shared/app_types.h
@@ -0,0 +1,23 @@
+// 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_SHARED_APP_TYPES_H_
+#define ASH_SHARED_APP_TYPES_H_
+
+namespace ash {
+
+// App type of the window. This enum is used to back
+// an UMA histogram and should be treated as append-only.
+enum class AppType {
+  OTHERS = 0,
+  BROWSER,
+  CHROME_APP,
+  ARC_APP,
+  DEFAULT_NOTE_TAKING_APP,

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

Why the DEFAULT_ here instead of NOTE_TAKING_APP?

[Daniel Erat, 2016/09/27 23:34:09]

i'm fine with dropping the DEFAULT_ here. (as background, there will be a
setting by which the user can select a note-taking app that will be launched in
various places in the UI.)

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

Thanks for the explanation.

+  APP_COUNT,

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

I would prefer you define a constant outside the enum for this. That way anyone
wanting to handle a switch statement doesn't have to deal with APP_COUNT.

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

Done.

+};
+
+}  // namespace ash
+
+#endif  // ASH_SHARED_APP_TYPES_H_