Revert "Move ExtensionCache to //extensions"

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 696 matching lines @@
         'browser/script_executor.cc',
         'browser/script_executor.h',
         'browser/stash_backend.cc',
         'browser/stash_backend.h',
         'browser/state_store.cc',
         'browser/state_store.h',
         'browser/suggest_permission_util.cc',
         'browser/suggest_permission_util.h',
         'browser/uninstall_reason.h',
         'browser/update_observer.h',
-        'browser/updater/extension_cache.h',
         'browser/updater/manifest_fetch_data.cc',
         'browser/updater/manifest_fetch_data.h',
-        'browser/updater/null_extension_cache.cc',
-        'browser/updater/null_extension_cache.h',
         'browser/updater/safe_manifest_parser.cc',
         'browser/updater/safe_manifest_parser.h',
         'browser/url_request_util.cc',
         'browser/url_request_util.h',
         'browser/value_store/leveldb_value_store.cc',
         'browser/value_store/leveldb_value_store.h',
         'browser/value_store/testing_value_store.cc',
         'browser/value_store/testing_value_store.h',
         'browser/value_store/value_store.cc',
         'browser/value_store/value_store.h',
@@ skipping 456 matching lines @@
       'conditions': [
         ['OS=="win" and win_use_allocator_shim==1', {
           'dependencies': [
             '../base/allocator/allocator.gyp:allocator',
           ],
         }],
       ],
     },
   ]
 }