Use mojo SystemTray interfaces for both mash and classic ash

ash/common/system/tray/system_tray_controller.h

Index: ash/common/system/tray/system_tray_controller.h
diff --git a/ash/common/system/tray/system_tray_controller.h b/ash/common/system/tray/system_tray_controller.h
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index 0000000000000000000000000000000000000000..a229b7e5711f3b0e4350bff3ffb0734486195b70
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+++ b/ash/common/system/tray/system_tray_controller.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 ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_CONTROLLER_H_
+#define ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_CONTROLLER_H_
+
+#include "ash/public/interfaces/system_tray.mojom.h"
+#include "base/i18n/time_formatting.h"
+#include "base/macros.h"
+#include "base/observer_list.h"
+
+namespace shell {
+class Connector;
+}
+
+namespace ash {
+
+class ClockObserver;
+
+// Allows control of the system tray the mojom::SystemTray interface. Provides
+// caching of state pushed down from chrome browser. Provides a wrapper around
+// the mojom::SystemTrayClient interface that handles retries.
+//
+// TODO: What about tests? How would you mock one of these?
+//
+// TODO: Delete SystemTrayDelegateMus
+// This would be called "SystemTray" but we already have one of those.
+class SystemTrayController : public mojom::SystemTray {
+ public:
+  explicit SystemTrayController(shell::Connector* connector);
+  ~SystemTrayController() override;
+
+  // REVIEWERS: Methods migrated from SystemTrayDelegate.
+  base::HourClockType GetHourClockType() const;
+  void ShowDateSettings();
+
+  // TODO: Migrate other observers from SystemTrayNotifier.
+  void AddClockObserver(ClockObserver* observer);
+  void RemoveClockObserver(ClockObserver* observer);
+
+ private:
+  // Connects or reconnects to the mojom::SystemTrayClient interface and returns
+  // the interface pointer.
+  mojom::SystemTrayClient* ConnectToSystemTrayClient();
+
+  // Handles errors on the |system_tray_client_| interface connection.
+  void OnClientConnectionError();
+
+   // mojom::SystemTray:
+  void SetUse24HourClock(bool use_24_hour) override;
+
+  // May be null in unit tests.
+  shell::Connector* connector_;
+
+  // Client interface in chrome browser.
+  mojom::SystemTrayClientPtr system_tray_client_;
+
+  // 12 or 24 hour display.
+  base::HourClockType hour_clock_type_;
+
+  base::ObserverList<ClockObserver> clock_observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemTrayController);
+};
+
+}  // namspace ash
+
+#endif  // ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_CONTROLLER_H_