Hook up the FocusController behind a flag.

ui/views/widget/native_widget_aura_window_observer.h

Index: ui/views/widget/native_widget_aura_window_observer.h
===================================================================
--- ui/views/widget/native_widget_aura_window_observer.h	(revision 170620)
+++ ui/views/widget/native_widget_aura_window_observer.h	(working copy)
@@ -6,9 +6,9 @@
 #define UI_VIEWS_WIDGET_NATIVE_WIDGET_AURA_WINDOW_OBSERVER_H_
 
 #include "base/compiler_specific.h"
-#include "ui/aura/client/activation_change_observer.h"
 #include "ui/aura/window_observer.h"
 #include "ui/gfx/native_widget_types.h"
+#include "ui/views/corewm/activation_change_shim.h"
 #include "ui/views/widget/native_widget_private.h"
 
 namespace views {
@@ -18,7 +18,7 @@
 // changes in such a way that we should enable inactive rendering.
 class NativeWidgetAuraWindowObserver
     : public aura::WindowObserver,
-      public aura::client::ActivationChangeObserver {
+      public corewm::ActivationChangeShim {
  public:
   explicit NativeWidgetAuraWindowObserver(
       gfx::NativeView native_view,