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
new file mode 100644
index 0000000000000000000000000000000000000000..f3b8800e471a24ce834ce523f2d74c8b4a723199
--- /dev/null
+++ b/ash/common/system/tray/system_tray_controller.h
@@ -0,0 +1,72 @@
+// 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 "mojo/public/cpp/bindings/binding_set.h"
+
+namespace shell {
+class Connector;
+}
+
+namespace ash {
+
+// Both implements mojom::SystemTray and wraps the mojom::SystemTrayClient
+// interface. The wrapper makes the initial connection and handles reconnecting
+// on error. Implements both because it caches state pushed down from the
+// browser process via SystemTray so it can be synchronously queried inside ash.
+//
+// Conceptually similar to historical ash-to-chrome interfaces like
+// SystemTrayDelegate. Lives on the main thread.
+//
+// Only connects to the actual mojom::SystemTrayClient interface when running on
+// Chrome OS. In tests and on Windows all operations are no-ops.
+//
+// TODO: Consider renaming this to SystemTrayClient or renaming the current
+// SystemTray to SystemTrayView and making this class SystemTray.
+class SystemTrayController : public mojom::SystemTray {
+ public:
+  explicit SystemTrayController(shell::Connector* connector);
+  ~SystemTrayController() override;
+
+  // Wrappers around the mojom::SystemTrayClient interface.
+  base::HourClockType hour_clock_type() const { return hour_clock_type_; }
+  void ShowDateSettings();
+
+  // Binds the mojom::SystemTray interface to this object.
+  void BindRequest(mojom::SystemTrayRequest request);

[Ken Rockot(use gerrit already), 2016/10/03 18:19:03]

Then again... if you keep MojoInterfaceFactory as a class, you could make it a
friend of SystemTrayController and hide this method.

+
+ private:
+  // Connects or reconnects to the mojom::SystemTrayClient interface when
+  // running on Chrome OS. Otherwise does nothing. Returns true if connected.
+  bool 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. Only bound on Chrome OS.
+  mojom::SystemTrayClientPtr system_tray_client_;
+
+  // Bindings for the SystemTray interface.
+  mojo::BindingSet<mojom::SystemTray> bindings_;
+
+  // The type of clock hour display: 12 or 24 hour.
+  base::HourClockType hour_clock_type_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemTrayController);
+};
+
+}  // namspace ash
+
+#endif  // ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_CONTROLLER_H_