Allow dynamic enabling/disabling of unified desktop

ash/display/window_tree_host_manager.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/display/window_tree_host_manager.h"
 
 #include <algorithm>
 #include <cmath>
 #include <map>
 
@@ skipping 823 matching lines @@
 void WindowTreeHostManager::PostDisplayConfigurationChange() {
   if (limiter_)
     limiter_->SetThrottleTimeout(kAfterDisplayChangeThrottleTimeoutMs);
 
   focus_activation_store_->Restore();
 
   DisplayManager* display_manager = GetDisplayManager();
   DisplayLayoutStore* layout_store = display_manager->layout_store();
   if (display_manager->num_connected_displays() > 1) {
     DisplayIdPair pair = display_manager->GetCurrentDisplayIdPair();
+    DisplayLayout layout = layout_store->GetRegisteredDisplayLayout(pair);
     layout_store->UpdateMultiDisplayState(
-        pair, display_manager->IsInMirrorMode(),
-        display_manager->default_multi_display_mode() ==
-            DisplayManager::UNIFIED);
+        pair, display_manager->IsInMirrorMode(), layout.default_unified);
 
     if (Shell::GetScreen()->GetNumDisplays() > 1) {
-      DisplayLayout layout = layout_store->GetRegisteredDisplayLayout(pair);
       int64 primary_id = layout.primary_id;
       SetPrimaryDisplayId(primary_id == gfx::Display::kInvalidDisplayID
                               ? pair.first
                               : primary_id);
       // Update the primary_id in case the above call is
       // ignored. Happens when a) default layout's primary id
       // doesn't exist, or b) the primary_id has already been
       // set to the same and didn't update it.
       layout_store->UpdatePrimaryDisplayId(
           pair, Shell::GetScreen()->GetPrimaryDisplay().id());
@@ skipping 65 matching lines @@
       ->display_configurator_animation()
       ->StartFadeInAnimation();
 #endif
 }
 
 void WindowTreeHostManager::SetMirrorModeAfterAnimation(bool mirror) {
   GetDisplayManager()->SetMirrorMode(mirror);
 }
 
 }  // namespace ash