Auto open and close the palette on an eject event.

ash/common/system/chromeos/palette/eject_controller.h

Index: ash/common/system/chromeos/palette/eject_controller.h
diff --git a/ash/common/system/chromeos/palette/eject_controller.h b/ash/common/system/chromeos/palette/eject_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..2e6d2983a50a1f04579b2083bbd1349ecb13e5e9
--- /dev/null
+++ b/ash/common/system/chromeos/palette/eject_controller.h
@@ -0,0 +1,34 @@
+// 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_COMMON_SYSTEM_CHROMEOS_PALETTE_EJECT_CONTROLLER_H_
+#define ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_EJECT_CONTROLLER_H_
+
+#include "ash/ash_export.h"
+#include "base/callback.h"
+#include "base/macros.h"
+#include "ui/events/devices/input_device_event_observer.h"
+
+namespace ash {
+
+// This class observes input device changes for the palette.
+class ASH_EXPORT EjectController : public ui::InputDeviceEventObserver {
+ public:
+  using OnEjectCallback = base::Callback<void(bool)>;
+
+  EjectController(const OnEjectCallback& on_eject);
+  ~EjectController() override;
+
+ private:
+  // ui::InputDeviceObserver:
+  void OnStylusEject() override;
+
+  OnEjectCallback on_eject_;
+
+  DISALLOW_COPY_AND_ASSIGN(EjectController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_SYSTEM_CHROMEOS_PALETTE_EJECT_CONTROLLER_H_