Mojo: add support for disallowing sync calls for a process.

mojo/public/c/system/thunks.cc

Index: mojo/public/c/system/thunks.cc
diff --git a/mojo/public/c/system/thunks.cc b/mojo/public/c/system/thunks.cc
index 1960dd6065f4fdd7d67e6557112ea9130aede75c..d6bfd95d1741c3b65581ca4a5818effc905673a3 100644
--- a/mojo/public/c/system/thunks.cc
+++ b/mojo/public/c/system/thunks.cc
@@ -282,6 +282,11 @@ MojoResult MojoNotifyBadMessage(MojoMessageHandle message,
   return g_thunks.NotifyBadMessage(message, error, error_num_bytes);
 }
 
+MojoResult MojoGetProperty(MojoPropertyType type, void* value) {
+  assert(g_thunks.GetProperty);
+  return g_thunks.GetProperty(type, value);
+}
+
 }  // extern "C"
 
 size_t MojoEmbedderSetSystemThunks(const MojoSystemThunks* system_thunks) {