Convert GN visibility to be a list.

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.
 
 pdf_use_skia = false
 
 config("pdfium_config") {
   cflags = []
   defines = [
     "FOXIT_CHROME_BUILD",
@@ skipping 98 matching lines @@
   if (is_win) {
     libs += [ "advapi32.lib", "gdi32.lib", "user32.lib" ]
   }
 
   if (is_mac) {
     libs += [ "AppKit.framework", "CoreFoundation.framework" ]
   }
 }
 
 # Targets below this are only visible within this file.
-visibility = ":*"
+visibility = [ ":*" ]
 
 component("safemath") {
   sources = [
     "third_party/logging.h",
     "third_party/macros.h",
     "third_party/template_util.h",
     "third_party/numerics/safe_conversions.h",
     "third_party/numerics/safe_conversions_impl.h",
     "third_party/numerics/safe_math.h",
     "third_party/numerics/safe_math_impl.h",
@@ skipping 729 matching lines @@
     "fpdfsdk/src/formfiller/FFL_RadioButton.cpp",
     "fpdfsdk/src/formfiller/FFL_TextField.cpp",
     "fpdfsdk/src/formfiller/FFL_Utils.cpp",
   ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   if (is_posix) {
     configs -= [ "//build/config/gcc:no_exceptions" ]
   }
   configs += [ ":pdfium_config", "//build/config/compiler:no_chromium_code" ]
 }