Create a mirror window.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 0415be4e43fc20a043f29f0adfb435843fe36b47..b663f78c655bbb0f8dc02a28768c85490c7a761c 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -110,6 +110,7 @@ class EventClientImpl;
 class EventRewriterEventFilter;
 class EventTransformationHandler;
 class FocusCycler;
+class MirrorWindowController;
 class MouseCursorEventFilter;
 class OutputConfiguratorAnimation;
 class OverlayEventFilter;
@@ -284,6 +285,9 @@ class ASH_EXPORT Shell
   internal::DisplayManager* display_manager() {
     return display_manager_.get();
   }
+  internal::MirrorWindowController* mirror_window_controller() {
+    return mirror_window_controller_.get();
+  }
   views::corewm::InputMethodEventFilter* input_method_filter() {
     return input_method_filter_.get();
   }
@@ -572,6 +576,7 @@ class ASH_EXPORT Shell
   scoped_ptr<views::corewm::InputMethodEventFilter> input_method_filter_;
 
   scoped_ptr<internal::DisplayManager> display_manager_;
+  scoped_ptr<internal::MirrorWindowController> mirror_window_controller_;
 
 #if defined(OS_CHROMEOS) && defined(USE_X11)
   // Controls video output device state.