Remove unused class UnsafePersistent.

extensions/extensions.gyp

 # Copyright 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 383 matching lines @@
     {
       'target_name': 'extensions_renderer',
       'type': 'static_library',
       'include_dirs': [
         '..',
       ],
       'sources': [
         'renderer/native_handler.cc',
         'renderer/native_handler.h',
         'renderer/scoped_persistent.h',
-        'renderer/unsafe_persistent.h',
       ],
       'dependencies': [
         '../third_party/WebKit/public/blink.gyp:blink',
       ],
       # Disable c4267 warnings until we fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
     },
     {
       'target_name': 'extensions_test_support',
       'type': 'static_library',
@@ skipping 49 matching lines @@
         'common/one_shot_event_unittest.cc',
         'common/permissions/api_permission_set_unittest.cc',
         'common/permissions/manifest_permission_set_unittest.cc',
         'common/url_pattern_set_unittest.cc',
         'common/url_pattern_unittest.cc',
         'common/user_script_unittest.cc',
       ],
     },
   ]
 }