Introducing gpu::CommandBufferId as a distinct, IdType<...>-based type.

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 bff1f7016b00ee31650e74a1f6018c1f4186e882..8c624779182e43c40ca130d73d3c6a552f9eb03a 100644
--- a/mojo/converters/surfaces/surfaces_type_converters.cc
+++ b/mojo/converters/surfaces/surfaces_type_converters.cc
@@ -543,7 +543,7 @@ SyncTokenPtr TypeConverter<SyncTokenPtr, gpu::SyncToken>::Convert(
   sync_token->namespace_id =
       static_cast<CommandBufferNamespace>(input.namespace_id());
   sync_token->extra_data_field = input.extra_data_field();
-  sync_token->command_buffer_id = input.command_buffer_id();
+  sync_token->command_buffer_id = input.command_buffer_id().GetUnsafeValue();
   sync_token->release_count = input.release_count();
   return sync_token;
 }
@@ -553,8 +553,10 @@ gpu::SyncToken TypeConverter<gpu::SyncToken, SyncTokenPtr>::Convert(
     const SyncTokenPtr& input) {
   const gpu::CommandBufferNamespace namespace_id =
       static_cast<gpu::CommandBufferNamespace>(input->namespace_id);
-  gpu::SyncToken sync_token(namespace_id, input->extra_data_field,
-                            input->command_buffer_id, input->release_count);
+  gpu::SyncToken sync_token(
+      namespace_id, input->extra_data_field,
+      gpu::CommandBufferId::FromUnsafeValue(input->command_buffer_id),
+      input->release_count);
   if (input->verified_flush)
     sync_token.SetVerifyFlush();