Add three missing test files to gn builds

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.
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 # GYP version: components/safe_json.gypi:safe_json
 source_set("safe_json") {
@@ skipping 33 matching lines @@
       "//ipc",
     ]
   }
 }
 
 # GYP version: components/safe_json.gypi:safe_json_unittest_sources
 source_set("unit_tests") {
   testonly = true
   sources = [
     "json_sanitizer_unittest.cc",
+    "testing_json_parser_unittest.cc",
   ]
 
   deps = [
     ":safe_json",
     ":test_support",
     "//base",
     "//testing/gtest",
   ]
 }
 
@@ skipping 34 matching lines @@
   ]
 
   deps = [
     ":messages",
     "//base",
     "//content/public/common",
     "//content/public/utility",
     "//ipc",
   ]
 }