Make base a static ibrary

base/json/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("//build/config/nacl/config.gni")
 
-source_set("json") {
+# Should be static library, see documentation on //base:base for discussion.
+static_library("json") {
   sources = [
     "json_file_value_serializer.cc",
     "json_file_value_serializer.h",
     "json_parser.cc",
     "json_parser.h",
     "json_reader.cc",
     "json_reader.h",
     "json_string_value_serializer.cc",
     "json_string_value_serializer.h",
     "json_value_converter.cc",
@@ skipping 12 matching lines @@
   }
 
   configs += [ "//base:base_implementation" ]
 
   deps = [
     "//base/memory",
   ]
 
   visibility = [ "//base/*" ]
 }