Move DisplayList to display; add ScreenBase.

ash/test/display_manager_test_api.cc

Index: ash/test/display_manager_test_api.cc
diff --git a/ash/test/display_manager_test_api.cc b/ash/test/display_manager_test_api.cc
index a8ced5e6437f72d17d54ec09d04d15edefcd5cd4..e69615e08e7b2002c540f3f7dcee14611737ba4d 100644
--- a/ash/test/display_manager_test_api.cc
+++ b/ash/test/display_manager_test_api.cc
@@ -36,7 +36,7 @@ DisplayInfoList CreateDisplayInfoListFromString(
       specs, ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
   size_t index = 0;
 
-  display::DisplayList list =
+  display::Displays list =
       display_manager->IsInUnifiedMode()
           ? display_manager->software_mirroring_display_list()
           : display_manager->active_display_list();