Try to enable software mirror mode in UI message loop after Init()

ash/shell.cc

 // Copyright (c) 2012 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/shell.h"
 
 #include <algorithm>
 #include <string>
 
 #include "ash/accelerators/accelerator_controller.h"
@@ skipping 603 matching lines @@
 
   if (initially_hide_cursor_)
     cursor_manager_.HideCursor();
   cursor_manager_.SetCursor(ui::kCursorPointer);
 
   if (!cursor_manager_.IsCursorVisible()) {
     // Cursor might have been hidden by something other than chrome.
     // Let the first mouse event show the cursor.
     env_filter_->set_cursor_hidden_by_filter(true);
   }
+
+  // The compositor thread and main message loop have to be running in
+  // order to create mirror window. Run it after the main message loop
+  // is started.
+  base::MessageLoopForUI::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&internal::DisplayManager::CreateMirrorWindowIfAny,
+                 base::Unretained(display_manager_.get())));
 }
 
 void Shell::ShowContextMenu(const gfx::Point& location_in_screen,
                             ui::MenuSourceType source_type) {
   // No context menus if there is no session with an active user.
   if (!session_state_delegate_->NumberOfLoggedInUsers())
     return;
   // No context menus when screen is locked.
   if (session_state_delegate_->IsScreenLocked())
     return;
@@ skipping 323 matching lines @@
 ////////////////////////////////////////////////////////////////////////////////
 // Shell, aura::client::ActivationChangeObserver implementation:
 
 void Shell::OnWindowActivated(aura::Window* gained_active,
                               aura::Window* lost_active) {
   if (gained_active)
     target_root_window_ = gained_active->GetRootWindow();
 }
 
 }  // namespace ash