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

cc/surfaces/display_scheduler.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 "cc/surfaces/display_scheduler.h"
 
 #include <vector>
 
 #include "base/stl_util.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 63 matching lines @@
   TRACE_EVENT0("cc", "DisplayScheduler::SetNewRootSurface");
   root_surface_id_ = root_surface_id;
   SurfaceDamaged(root_surface_id);
 }
 
 // Indicates that there was damage to one of the surfaces.
 // Has some logic to wait for multiple active surfaces before
 // triggering the deadline.
 void DisplayScheduler::SurfaceDamaged(SurfaceId surface_id) {
   TRACE_EVENT1("cc", "DisplayScheduler::SurfaceDamaged", "surface_id",
-               surface_id.id);
+               surface_id.GetUnsafeValue());
 
   needs_draw_ = true;
 
   if (surface_id == root_surface_id_) {
     root_surface_damaged_ = true;
     expecting_root_surface_damage_because_of_resize_ = false;
   } else {
     child_surface_ids_damaged_.insert(surface_id);
 
     // TODO(mithro): Use hints from SetNeedsBeginFrames and SwapAborts.
@@ skipping 194 matching lines @@
 }
 
 void DisplayScheduler::DidSwapBuffersComplete() {
   pending_swaps_--;
   TRACE_EVENT1("cc", "DisplayScheduler::DidSwapBuffersComplete",
                "pending_frames", pending_swaps_);
   ScheduleBeginFrameDeadline();
 }
 
 }  // namespace cc