Convert GN visibility variables to lists.

build/toolchain/win/midl.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.
 
 assert(is_win)
 
 import("//build/config/win/visual_studio_version.gni")
 
 # This template defines a rule to invoke the MS IDL compiler.
 #
@@ skipping 19 matching lines @@
     out_dir = target_gen_dir
   }
 
   header_file = "{{source_name_part}}.h"
   dlldata_file = "{{source_name_part}}.dlldata.c"
   interface_identifier_file = "{{source_name_part}}_i.c"
   proxy_file = "{{source_name_part}}_p.c"
   type_library_file = "{{source_name_part}}.tlb"
 
   action_foreach(action_name) {
-    visibility = ":$source_set_name"
+    visibility = [ ":$source_set_name" ]
 
     # This functionality is handled by the win-tool because the GYP build has
     # MIDL support built-in.
     # TODO(brettw) move this to a separate MIDL wrapper script for better
     # clarity once GYP support is not needed.
     script = "$root_build_dir/gyp-win-tool"
 
     sources = invoker.sources
 
     # Note that .tlb is not included in the outputs as it is not always
@@ skipping 40 matching lines @@
     }
 
     # We only compile the IID files from the IDL tool rather than all outputs.
     sources = process_file_template(
         invoker.sources,
         [ "$out_dir/$interface_identifier_file" ])
 
     deps = [ ":$action_name" ]
   }
 }