Relocate display_manager from ash to ui

ui/display/BUILD.gn

Index: ui/display/BUILD.gn
diff --git a/ui/display/BUILD.gn b/ui/display/BUILD.gn
index 9faf6f487d2fdf100b6d4701a1a1a3fa007955de..f819cc2c8dd72d05658ce196436543c8960ea28b 100644
--- a/ui/display/BUILD.gn
+++ b/ui/display/BUILD.gn
@@ -48,6 +48,8 @@ component("display") {
     "manager/display_layout_builder.h",
     "manager/display_layout_store.cc",
     "manager/display_layout_store.h",
+    "manager/display_manager.cc",
+    "manager/display_manager.h",
     "manager/display_manager_utilities.cc",
     "manager/display_manager_utilities.h",
     "manager/managed_display_info.cc",
@@ -159,6 +161,8 @@ static_library("test_support") {
     "chromeos/test/test_display_layout_manager.h",
     "chromeos/test/test_native_display_delegate.cc",
     "chromeos/test/test_native_display_delegate.h",
+    "test/display_manager_test_api.cc",
+    "test/display_manager_test_api.h",
     "test/display_matchers.cc",
     "test/display_matchers.h",
     "test/display_test_util.h",