Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ash/system/chromeos/tray_display.h

Index: ash/system/chromeos/tray_display.h
diff --git a/ash/system/chromeos/tray_display.h b/ash/system/chromeos/tray_display.h
index 77994b62b2cfd8750325cffb66c8416bd0b89785..0685a9de29dc3c50e2b5e44f3c86256a80ad8532 100644
--- a/ash/system/chromeos/tray_display.h
+++ b/ash/system/chromeos/tray_display.h
@@ -7,7 +7,7 @@
 
 #include "ash/system/tray/system_tray_item.h"
 #include "base/memory/scoped_ptr.h"
-#include "ui/aura/display_observer.h"
+#include "ui/gfx/display_observer.h"
 
 #include "chromeos/display/output_configurator.h"
 
@@ -22,7 +22,7 @@ class DisplayView;
 
 class TrayDisplay : public SystemTrayItem,
                     public chromeos::OutputConfigurator::Observer,
-                    public aura::DisplayObserver {
+                    public gfx::DisplayObserver {
  public:
   TrayDisplay();
   virtual ~TrayDisplay();