Support private values in GN.

tools/gn/function_set_defaults.cc

Index: tools/gn/function_set_defaults.cc
diff --git a/tools/gn/function_set_defaults.cc b/tools/gn/function_set_defaults.cc
index ac61fe9853fa2690eb6dd7a6f6944955a9a3540d..785111311dea53399afcab66913eaaea10a852aa 100644
--- a/tools/gn/function_set_defaults.cc
+++ b/tools/gn/function_set_defaults.cc
@@ -84,7 +84,7 @@ Value RunSetDefaults(Scope* scope,
   // Now copy the values set on the scope we made into the free-floating one
   // (with no containing scope) used to hold the target defaults.
   Scope* dest = scope->MakeTargetDefaults(target_type);
-  block_scope.NonRecursiveMergeTo(dest, false, function,
+  block_scope.NonRecursiveMergeTo(dest, Scope::MergeOptions(), function,
                                   "<SHOULD NOT FAIL>", err);
   return Value();
 }