Use mojo SystemTray interfaces for both mash and classic ash

ash/mus/shell_delegate_mus.h

 // 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_MUS_SHELL_DELEGATE_MUS_H_
 #define ASH_MUS_SHELL_DELEGATE_MUS_H_
 
 #include <memory>
 
 #include "ash/common/shell_delegate.h"
 #include "ash/mus/app_list_presenter_mus.h"
 #include "base/macros.h"
 
 namespace shell {
 class Connector;
 }
 
 namespace ash {
 
 class ShellDelegateMus : public ShellDelegate {
  public:
   explicit ShellDelegateMus(shell::Connector* connector);
   ~ShellDelegateMus() override;
 
+  // ShellDelegate:
+  ::shell::Connector* GetShellConnector() const override;
   bool IsFirstRunAfterBoot() const override;
   bool IsIncognitoAllowed() const override;
   bool IsMultiProfilesEnabled() const override;
   bool IsRunningInForcedAppMode() const override;
   bool CanShowWindowForUser(WmWindow* window) const override;
   bool IsForceMaximizeOnFirstRun() const override;
   void PreInit() override;
   void PreShutdown() override;
   void Exit() override;
   keyboard::KeyboardUI* CreateKeyboardUI() override;
@@ skipping 16 matching lines @@
  private:
   shell::Connector* connector_;
   AppListPresenterMus app_list_presenter_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellDelegateMus);
 };
 
 }  // namespace ash
 
 #endif  // ASH_MUS_SHELL_DELEGATE_MUS_H_