Make JSONParser a pure interface.

components/safe_json.gypi

 # 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.
 
 {
   'targets': [
     {
       # GN version: //components/safe_json
       'target_name': 'safe_json',
       #'type': '<(component)',
       'type': 'static_library',
       'dependencies': [
         'safe_json_parser_message_filter',
         '../base/base.gyp:base',
         '../components/components_strings.gyp:components_strings',
         '../content/content.gyp:content_browser',
         '../ui/base/ui_base.gyp:ui_base',
       ],
       'include_dirs': [
         '..',
       ],
       'defines': [
         'SAFE_JSON_IMPLEMENTATION',
       ],
       'sources': [
         'safe_json/safe_json_parser.cc',
         'safe_json/safe_json_parser.h',
+        'safe_json/safe_json_parser_impl.cc',
+        'safe_json/safe_json_parser_impl.h',
       ],
     },
     {
+      'target_name': 'safe_json_test_support',
+      'type': 'static_library',
+      'dependencies': [
+        '../base/base.gyp:base',
+        ':safe_json',
+      ],
+      'include_dirs': [
+        '..',
+      ],
+      'sources': [
+        'safe_json/testing_json_parser.cc',
+        'safe_json/testing_json_parser.h',
+      ],
+    },
+    {
       'target_name': 'safe_json_parser_message_filter',
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
         '../content/content.gyp:content_browser',
         '../ipc/ipc.gyp:ipc',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'safe_json/safe_json_parser_message_filter.cc',
         'safe_json/safe_json_parser_message_filter.h',
         'safe_json/safe_json_parser_messages.cc',
         'safe_json/safe_json_parser_messages.h',
       ],
     },
   ],
 }