Write mojom and StructTraits for DisplaySnapshot.

ui/display/mojo/display_mode_struct_traits.h

 // Copyright 2017 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_MODE_STRUCT_TRAITS_H_
 #define UI_DISPLAY_MOJO_DISPLAY_MODE_STRUCT_TRAITS_H_
 
 #include "ui/display/types/display_mode.h"
 #include "ui/display/mojo/display_mode.mojom.h"
 #include "ui/gfx/geometry/size.h"
@@ skipping 12 matching lines @@
       const std::unique_ptr<display::DisplayMode>& display_mode) {
     return display_mode->is_interlaced();
   }
 
   static float refresh_rate(
       const std::unique_ptr<display::DisplayMode>& display_mode) {
     return display_mode->refresh_rate();
   }
 
   static bool Read(display::mojom::DisplayModeDataView data,
-                   std::unique_ptr<display::DisplayMode>* out) {
-    gfx::Size size;
-    if (!data.ReadSize(&size))
-      return false;
-    *out = base::MakeUnique<display::DisplayMode>(size, data.is_interlaced(),
-                                                  data.refresh_rate());
-    return true;
-  }
+                   std::unique_ptr<display::DisplayMode>* out);
 };
 
 }  // namespace mojo
 
 #endif  // UI_DISPLAY_MOJO_DISPLAY_MODE_STRUCT_TRAITS_H_