mash: Fix system tray clock 12/24 hour time setting

ash/public/interfaces/system_tray.mojom

+// 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.
+
+module ash.mojom;
+
+// Allows clients (e.g. Chrome browser) to control the ash system tray menu.
+interface SystemTray {
+  // Sets the clock to use 24 hour time formatting if |use_24_hour| is true.
+  // Otherwise sets 12 hour time formatting.
+  SetUse24HourClock(bool use_24_hour);

[Tom Sepez, 2016/09/20 16:34:42]

nit: do you want an enum in place of a bool?  Would there ever be some other
possibility?

[James Cook, 2016/09/20 16:42:57]

I looked at using an enum, but in this case the only setting is 12 vs. 24, and
that's what most of the existing C++ methods use, so I went with a bool.

I you feel strongly that I should use an enum ping me and I'll change it in a
followup CL.

+};
+
+// TODO(jamescook): SystemTrayDelegate to communicate from ash to chrome.