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

mojo/converters/surfaces/surfaces_type_converters.cc

Index: mojo/converters/surfaces/surfaces_type_converters.cc
diff --git a/mojo/converters/surfaces/surfaces_type_converters.cc b/mojo/converters/surfaces/surfaces_type_converters.cc
index f0a32bdb37345be225b2c6c2297231a0a3cd529c..b90a78d7ba697afc48963ee251e412aaa81f6f48 100644
--- a/mojo/converters/surfaces/surfaces_type_converters.cc
+++ b/mojo/converters/surfaces/surfaces_type_converters.cc
@@ -256,7 +256,7 @@ bool ConvertDrawQuad(const QuadPtr& input,
 SurfaceIdPtr TypeConverter<SurfaceIdPtr, cc::SurfaceId>::Convert(
     const cc::SurfaceId& input) {
   SurfaceIdPtr id(SurfaceId::New());
-  id->local = static_cast<uint32_t>(input.id);
+  id->local = static_cast<uint32_t>(input.GetUnsafeValue());
   id->id_namespace = cc::SurfaceIdAllocator::NamespaceForId(input);
   return id.Pass();
 }
@@ -267,7 +267,7 @@ cc::SurfaceId TypeConverter<cc::SurfaceId, SurfaceIdPtr>::Convert(
   uint64_t packed_id = input->id_namespace;
   packed_id <<= 32ull;
   packed_id |= input->local;
-  return cc::SurfaceId(packed_id);
+  return cc::SurfaceId::FromUnsafeValue(packed_id);
 }
 
 // static