Convert GN visibility variables to lists.

extensions/generated_extensions_api.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Defines a static library corresponding to the output of schema compiler tools
 # over a set of extensions API schemas (IDL or JSON format.) The library target
 # has implicit hard dependencies on all schema files listed by the invoker and
 # is itself a hard dependency.
 #
 # Invocations of this template may use the following variables:
@@ skipping 49 matching lines @@
   bundle_registration = defined(invoker.bundle_registration) &&
       invoker.bundle_registration
 
   schema_include_rules = ""
   if (defined(invoker.schema_include_rules)) {
     schema_include_rules = invoker.schema_include_rules
   }
 
   # Keep a copy of the target_name here since it will be trampled
   # in nested targets.
-  target_visibility = ":$target_name"
+  target_visibility = [ ":$target_name" ]
 
   generated_config_name = target_name + "_generated_config"
   config(generated_config_name) {
     include_dirs = [ target_gen_dir ]
     visibility = target_visibility
   }
 
   sources = invoker.sources
   root_namespace = invoker.root_namespace
 
@@ skipping 116 matching lines @@
     direct_dependent_configs = [ ":$generated_config_name" ]
 
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
     if (defined(invoker.output_name)) {
       output_name = invoker.output_name
     }
   }
 }