Move DisplayManager and DisplayChangeObserverX11 from aura to ash.

ui/gfx/screen_android.cc

Index: ui/gfx/screen_android.cc
diff --git a/ui/gfx/screen_android.cc b/ui/gfx/screen_android.cc
index 21116613727b7bbb832a8b1fab2a1c60224ef84a..a80582e077d22e1ff373c70f50f66cec6a534778 100644
--- a/ui/gfx/screen_android.cc
+++ b/ui/gfx/screen_android.cc
@@ -48,6 +48,14 @@ class ScreenAndroid : public Screen {
     return GetPrimaryDisplay();
   }
 
+  virtual void AddObserver(DisplayObserver* observer) OVERRIDE {
+    // no display change on Android.
+  }
+
+  virtual void RemoveObserver(DisplayObserver* observer) OVERRIDE {
+    // no display change on Android.
+  }
+
  private:
   DISALLOW_COPY_AND_ASSIGN(ScreenAndroid);
 };