Reusing base::IdType<...> to implement SurfaceId.

components/mus/ws/server_window_surface.cc

 // Copyright 2015 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.
 
 #include "components/mus/ws/server_window_surface.h"
 
 #include "cc/output/compositor_frame.h"
 #include "cc/quads/shared_quad_state.h"
 #include "cc/quads/surface_draw_quad.h"
 #include "components/mus/surfaces/surfaces_state.h"
@@ skipping 83 matching lines @@
   referenced_window_ids_.clear();
   return ConvertToCompositorFrame(input, this);
 }
 
 bool ServerWindowSurface::ConvertSurfaceDrawQuad(
     const mojom::QuadPtr& input,
     const mojom::CompositorFrameMetadataPtr& metadata,
     cc::SharedQuadState* sqs,
     cc::RenderPass* render_pass) {
   Id id = static_cast<Id>(
-      input->surface_quad_state->surface.To<cc::SurfaceId>().id);
+      input->surface_quad_state->surface.To<cc::SurfaceId>().GetUnsafeValue());
   WindowId other_window_id = WindowIdFromTransportId(id);
   ServerWindow* other_window = window()->GetChildWindow(other_window_id);
   if (!other_window) {
     DVLOG(2) << "The window ID '" << id << "' does not exist.";
     // TODO(fsamuel): We return true here so that the CompositorFrame isn't
     // entirely rejected. We just drop this SurfaceDrawQuad. This failure
     // can happen if the client has an out of date view of the window tree.
     // It would be nice if we can avoid reaching this state in the future.
     return true;
   }
@@ skipping 36 matching lines @@
 }
 
 void ServerWindowSurface::SetBeginFrameSource(
     cc::SurfaceId surface_id,
     cc::BeginFrameSource* begin_frame_source) {
   // TODO(tansell): Implement this.
 }
 
 }  // namespace ws
 }  // namespace mus