Convert GN visibility variables to lists.

third_party/protobuf/proto_library.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.
 
 # Compile a protocol buffer.
 #
 # Protobuf parameters:
 #
 #   proto_out_dir (optional)
 #       Specifies the path suffix that output files are generated under. This
@@ skipping 37 matching lines @@
 #      "foo.proto",
 #    ]
 #  }
 
 template("proto_library") {
   assert(defined(invoker.sources), "Need sources for proto_library")
 
   action_name = "${target_name}_gen"
   source_set_name = target_name
   action_foreach(action_name) {
-    visibility = ":$source_set_name"
+    visibility = [ ":$source_set_name" ]
 
     script = "//tools/protoc_wrapper/protoc_wrapper.py"
 
     sources = invoker.sources
 
     # Compute the output directory, both relative to the source root (for
     # declaring "outputs") and relative to the build dir (for passing to the
     # script).
     if (defined(invoker.proto_out_dir)) {
       # Put the results in the specified dir in the gen tree.
@@ skipping 76 matching lines @@
     deps = [
       ":$action_name",
       "//third_party/protobuf:protobuf_lite",
     ]
 
     # The generated headers reference headers within protobuf_lite, so
     # dependencies must be able to find those headers too.
     forward_dependent_configs_from = [ "//third_party/protobuf:protobuf_lite" ]
   }
 }