Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ui/views/widget/desktop_aura/desktop_screen_x11.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11.cc b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
index 9ce56a8c61878517317ab10a92428da78195b046..77dbaa497a79b926d93fd2fe4b896af09946cdde 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
@@ -47,6 +47,8 @@ class DesktopScreenX11 : public gfx::Screen {
   virtual gfx::Display GetDisplayMatching(
       const gfx::Rect& match_rect) const OVERRIDE;
   virtual gfx::Display GetPrimaryDisplay() const OVERRIDE;
+  virtual void AddObserver(gfx::DisplayObserver* observer) OVERRIDE;
+  virtual void RemoveObserver(gfx::DisplayObserver* observer) OVERRIDE;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DesktopScreenX11);
@@ -122,6 +124,15 @@ gfx::Display DesktopScreenX11::GetPrimaryDisplay() const {
   return gfx::Display(0, gfx::Rect(GetPrimaryDisplaySize()));
 }
 
+void DesktopScreenX11::AddObserver(gfx::DisplayObserver* observer) {
+  // TODO(erg|oshima): Do the right thing once we know what that is.
+  // crbug.com/122863
+}
+void DesktopScreenX11::RemoveObserver(gfx::DisplayObserver* observer) {
+  // TODO(erg|oshima): Do the right thing once we know what that is.
+  // crbug.com/122863
+}
+
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////