Change static library targets in safe_json GN files to source sets.

components/safe_json/BUILD.gn

 # Copyright 2015 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.
 
 # GYP version: components/safe_json.gypi:safe_json
-static_library("safe_json") {
+source_set("safe_json") {
   sources = [
     "safe_json_parser.cc",
     "safe_json_parser.h",
     "safe_json_parser_impl.cc",
     "safe_json_parser_impl.h",
   ]
 
-  defines = [ "SAFE_JSON_IMPLEMENTATION" ]
-
   deps = [
     ":safe_json_parser_message_filter",
     "//base",
     "//components/strings",
     "//content/public/browser",
     "//ui/base",
   ]
 }
 
 # GYP version: components/safe_json.gypi:safe_json_test_support
 source_set("test_support") {
   testonly = true
   sources = [
     "testing_json_parser.cc",
     "testing_json_parser.h",
   ]
 
   deps = [
     ":safe_json",
     "//base",
   ]
 }
 
 # GYP version: components/safe_json.gypi:safe_json_parser_message_filter
-static_library("safe_json_parser_message_filter") {
+source_set("safe_json_parser_message_filter") {
   sources = [
     "safe_json_parser_message_filter.cc",
     "safe_json_parser_message_filter.h",
     "safe_json_parser_messages.cc",
     "safe_json_parser_messages.h",
   ]
 
   deps = [
     "//base",
     "//content/public/browser",
     "//ipc",
   ]
 }