native_support service: SynchronousInterfacePtr conversion in tests.

services/native_support/BUILD.gn

Index: services/native_support/BUILD.gn
diff --git a/services/native_support/BUILD.gn b/services/native_support/BUILD.gn
index 276a086ad12c1bd6e4cb8c241790292246054cc9..b19b82f6c34d605a61768d5b823fd155cf979148 100644
--- a/services/native_support/BUILD.gn
+++ b/services/native_support/BUILD.gn
@@ -52,7 +52,10 @@ mojo_native_application("apptests") {
     "//mojo/services/files/cpp:files_impl",
     "//mojo/services/files/interfaces",
     "//mojo/services/native_support/interfaces",
+    "//mojo/services/native_support/interfaces:interfaces_sync",
   ]
 
-  data_deps = [ ":native_support($default_toolchain)" ]
+  data_deps = [
+    ":native_support($default_toolchain)",
+  ]
 }