Disable tracing in user service

services/user/user_shell_client.h

Index: services/user/user_shell_client.h
diff --git a/services/user/user_shell_client.h b/services/user/user_shell_client.h
index 283eb4ec5460c9afa413d98f72d2e9a596327b4f..8bd57b6eb21013521ed2cb1bd3e79d4c8338e6fe 100644
--- a/services/user/user_shell_client.h
+++ b/services/user/user_shell_client.h
@@ -11,7 +11,6 @@
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "services/shell/public/cpp/interface_factory.h"
 #include "services/shell/public/cpp/shell_client.h"
-#include "services/tracing/public/cpp/tracing_impl.h"
 #include "services/user/public/interfaces/user_service.mojom.h"
 
 namespace user_service {
@@ -53,8 +52,6 @@ class UserShellClient
   scoped_refptr<base::SingleThreadTaskRunner> user_service_runner_;
   scoped_refptr<base::SingleThreadTaskRunner> leveldb_service_runner_;
 
-  mojo::TracingImpl tracing_;
-
   // We create these two objects so we can delete them on the correct task
   // runners.
   class UserServiceObjects;