Create a mirror window.

ash/display/display_controller.cc

Index: ash/display/display_controller.cc
diff --git a/ash/display/display_controller.cc b/ash/display/display_controller.cc
index c2f981ff2b14178e020fe7b36b6dd20035647184..dd6307c13590acd12958239473a3de83664dad20 100644
--- a/ash/display/display_controller.cc
+++ b/ash/display/display_controller.cc
@@ -621,6 +621,10 @@ DisplayLayout DisplayController::GetRegisteredDisplayLayout(
 }
 
 void DisplayController::ToggleMirrorMode() {
+  internal::DisplayManager* display_manager = GetDisplayManager();
+  if (display_manager->num_connected_displays() <= 1)
+    return;
+
   if (limiter_) {
     if  (limiter_->IsThrottled())
       return;
@@ -628,15 +632,12 @@ void DisplayController::ToggleMirrorMode() {
   }
 #if defined(OS_CHROMEOS) && defined(USE_X11)
   Shell* shell = Shell::GetInstance();
-  internal::DisplayManager* display_manager = GetDisplayManager();
-  if (display_manager->num_connected_displays() > 1) {
-    internal::OutputConfiguratorAnimation* animation =
-        shell->output_configurator_animation();
-    animation->StartFadeOutAnimation(base::Bind(
-        base::IgnoreResult(&internal::DisplayManager::SetMirrorMode),
-        base::Unretained(display_manager),
-        !display_manager->IsMirrored()));
-  }
+  internal::OutputConfiguratorAnimation* animation =
+      shell->output_configurator_animation();
+  animation->StartFadeOutAnimation(base::Bind(
+      base::IgnoreResult(&internal::DisplayManager::SetMirrorMode),
+      base::Unretained(display_manager),
+      !display_manager->IsMirrored()));
 #endif
 }