Convert GN single-item list concat to use lists.

tools/gn/secondary/net/BUILD.gn

 # Copyright (c) 2013 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("//crypto/ssl/flags.gni")
 import("//tools/grit/grit_rule.gni")
 
 component("net") {
   external = true
   sources = [
@@ skipping 1091 matching lines @@
       "ssl/client_cert_store_nss.h",
     ]
     deps += [
       #"//net/third_party/nss:ssl",
       #"//third_party/nss:nspr",
       #"//third_party/nss:nss",
     ]
   }
 
   if (is_linux && use_nss) {
-    configs += "//third_party/nss:nss_linux_config"
+    configs += [ "//third_party/nss:nss_linux_config" ]
   }
 
   if (is_chromeos) {
     sources -= [
        "base/network_change_notifier_linux.cc",
        "base/network_change_notifier_linux.h",
        "proxy/proxy_config_service_linux.cc",
        "proxy/proxy_config_service_linux.h",
     ]
   }
@@ skipping 60 matching lines @@
       "socket/ssl_server_socket_openssl.cc",
       "ssl/openssl_client_key_store.cc",
       "ssl/openssl_client_key_store.h",
     ]
   }
 
   if (is_posix) {
     posix_avoid_mmap = false  # TODO(brettw) should be true on 32-bit Android.
     if (posix_avoid_mmap) {
       defines = [ "POSIX_AVOID_MMAP" ]
-      sources -= "disk_cache/mapped_file_posix.cc"
+      sources -= [ "disk_cache/mapped_file_posix.cc" ]
     } else {  # !posix_avoid_mmap
-      sources -= "disk_cache/mapped_file_avoid_mmap_posix.cc"
+      sources -= [ "disk_cache/mapped_file_avoid_mmap_posix.cc" ]
     }
   }
 }
 
 #grit("net_resources") {
 #  external = true
 #  source = "base/net_resources.grd"
 #}
 
 static_library("http_server") {
   external = true
   sources = [
     "server/http_connection.cc",
     "server/http_connection.h",
     "server/http_server.cc",
     "server/http_server.h",
     "server/http_server_request_info.cc",
     "server/http_server_request_info.h",
     "server/http_server_response_info.cc",
     "server/http_server_response_info.h",
     "server/web_socket.cc",
     "server/web_socket.h",
   ]
   configs += [ "//build/config/compiler:wexit_time_destructors" ]
   deps = [
     ":net",
     "//base",
   ]
 }