Remove DisplayStructTraitsTest interface.

ui/display/mojo/display_struct_traits.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_DISPLAY_MOJO_DISPLAY_STRUCT_TRAITS_H_
 #define UI_DISPLAY_MOJO_DISPLAY_STRUCT_TRAITS_H_
 
 #include "ui/display/display.h"
 #include "ui/display/mojo/display.mojom.h"
+#include "ui/gfx/geometry/mojo/geometry_struct_traits.h"
 
 namespace mojo {
 
 template <>
 struct EnumTraits<display::mojom::Rotation, display::Display::Rotation> {
   static display::mojom::Rotation ToMojom(display::Display::Rotation type);
   static bool FromMojom(display::mojom::Rotation type,
                         display::Display::Rotation* output);
 };
 
@@ skipping 34 matching lines @@
   static const gfx::Size& maximum_cursor_size(const display::Display& display) {
     return display.maximum_cursor_size();
   }
 
   static bool Read(display::mojom::DisplayDataView data, display::Display* out);
 };
 
 }  // namespace mojo
 
 #endif  // UI_DISPLAY_MOJO_DISPLAY_STRUCT_TRAITS_H_