mash: Add SystemTrayClient interface, use to show date settings

chrome/browser/ui/ash/system_tray_common.h

Index: chrome/browser/ui/ash/system_tray_common.h
diff --git a/chrome/browser/ui/webui/cast/cast_ui.h b/chrome/browser/ui/ash/system_tray_common.h
similarity index 33%
copy from chrome/browser/ui/webui/cast/cast_ui.h
copy to chrome/browser/ui/ash/system_tray_common.h
index 2cae6ddb4761b92156792bc4cae96211ff8307f2..1caffc87536911893cbb7c9b77b40e6460544f1e 100644
--- a/chrome/browser/ui/webui/cast/cast_ui.h
+++ b/chrome/browser/ui/ash/system_tray_common.h
@@ -2,20 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CHROME_BROWSER_UI_WEBUI_CAST_CAST_UI_H_
-#define CHROME_BROWSER_UI_WEBUI_CAST_CAST_UI_H_
+#ifndef CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_COMMON_H_
+#define CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_COMMON_H_
 
 #include "base/macros.h"
-#include "base/values.h"
-#include "content/public/browser/web_ui_controller.h"
 
-// The WebUI for chrome://cast
-class CastUI : public content::WebUIController {
+// System tray code shared between classic ash SystemTrayDelegateChromeos and
+// mustash SystemTrayClient.
+class SystemTrayCommon {
  public:
-  explicit CastUI(content::WebUI* web_ui);
-  ~CastUI() override;
+  // Shows the settings related to date, timezone etc.
+  static void ShowDateSettings();
+
  private:
-  DISALLOW_COPY_AND_ASSIGN(CastUI);
+  DISALLOW_IMPLICIT_CONSTRUCTORS(SystemTrayCommon);
 };
 
-#endif  // CHROME_BROWSER_UI_WEBUI_CAST_CAST_UI_H_
+#endif  // CHROME_BROWSER_UI_ASH_SYSTEM_TRAY_COMMON_H_