Use mojo SystemTray interfaces for both mash and classic ash

ash/aura/wm_shell_aura.cc

 // 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.
 
 #include "ash/aura/wm_shell_aura.h"
 
 #include <utility>
 
 #include "ash/aura/key_event_watcher_aura.h"
 #include "ash/aura/pointer_watcher_adapter.h"
@@ skipping 59 matching lines @@
     Shell::GetInstance()->activation_client()->RemoveObserver(this);
 
   if (added_display_observer_)
     Shell::GetInstance()->window_tree_host_manager()->RemoveObserver(this);
 
   pointer_watcher_adapter_.reset();
 
   WmShell::Shutdown();
 }
 
+bool WmShellAura::IsRunningInMash() const {
+  return false;
+}
+
 WmWindow* WmShellAura::NewWindow(ui::wm::WindowType window_type,
                                  ui::LayerType layer_type) {
   aura::Window* aura_window = new aura::Window(nullptr);
   aura_window->SetType(window_type);
   aura_window->Init(layer_type);
   return WmWindowAura::Get(aura_window);
 }
 
 WmWindow* WmShellAura::GetFocusedWindow() {
   return WmWindowAura::Get(
@@ skipping 230 matching lines @@
   FOR_EACH_OBSERVER(WmDisplayObserver, display_observers_,
                     OnDisplayConfigurationChanging());
 }
 
 void WmShellAura::OnDisplayConfigurationChanged() {
   FOR_EACH_OBSERVER(WmDisplayObserver, display_observers_,
                     OnDisplayConfigurationChanged());
 }
 
 }  // namespace ash