Convert GN visibility to lists.

Source/modules/BUILD.gn

 # 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.
 
 import("//third_party/WebKit/Source/bindings/bindings.gni")
 import("//third_party/WebKit/Source/bindings/modules/v8/generated.gni")
 import("//third_party/WebKit/Source/bindings/modules/v8/v8.gni")
 import("//third_party/WebKit/Source/build/make_file_arrays.gni")
 import("//third_party/WebKit/Source/build/scripts/scripts.gni")
 import("//third_party/WebKit/Source/modules/modules.gni")
 
-visibility = "//third_party/WebKit/Source/*"
+visibility = [ "//third_party/WebKit/Source/*" ]
 
 # GYP version: WebKit/Source/modules/modules.gyp:modules
 source_set("modules") {
-  visibility = "//third_party/WebKit/*"
+  visibility = []  # Allow re-assignment of list.
+  visibility = [ "//third_party/WebKit/*" ]
 
   sources = rebase_path(modules_files, ".", "//")
   sources += bindings_modules_v8_files
   sources += rebase_path(bindings_modules_generated_aggregate_files, ".", "//")
 
   if (!is_win) {
     sources -= [
       "webdatabase/sqlite/SQLiteFileSystemWin.cpp",
     ]
   }
@@ skipping 56 matching lines @@
 }
 
 # GYP version: WebKit/Source/modules/modules_generated.gyp:make_modules_generated
 group("make_modules_generated") {
   deps = [
     "//third_party/WebKit/Source/core:core_event_interfaces",
     "//third_party/WebKit/Source/bindings/modules:bindings_modules_generated",
     ":module_names",
   ]
 }