Implement offline mode behind a flag

content/content_browser.gypi

 # Copyright (c) 2012 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.
 
 {
   'dependencies': [
     'browser/speech/proto/speech_proto.gyp:speech_proto',
     '../base/base.gyp:base_static',
     '../crypto/crypto.gyp:crypto',
     '../google_apis/google_apis.gyp:google_apis',
@@ skipping 532 matching lines @@
     'browser/loader/buffered_resource_handler.cc',
     'browser/loader/buffered_resource_handler.h',
     'browser/loader/certificate_resource_handler.cc',
     'browser/loader/certificate_resource_handler.h',
     'browser/loader/cross_site_resource_handler.cc',
     'browser/loader/cross_site_resource_handler.h',
     'browser/loader/doomed_resource_handler.cc',
     'browser/loader/doomed_resource_handler.h',
     'browser/loader/layered_resource_handler.cc',
     'browser/loader/layered_resource_handler.h',
+    'browser/loader/offline_manager.cc',
+    'browser/loader/offline_manager.h',
     'browser/loader/power_save_block_resource_throttle.cc',
     'browser/loader/power_save_block_resource_throttle.h',
     'browser/loader/redirect_to_file_resource_handler.cc',
     'browser/loader/redirect_to_file_resource_handler.h',
     'browser/loader/render_view_host_tracker.cc',
     'browser/loader/render_view_host_tracker.h',
     'browser/loader/resource_buffer.cc',
     'browser/loader/resource_buffer.h',
     'browser/loader/resource_dispatcher_host_impl.cc',
     'browser/loader/resource_dispatcher_host_impl.h',
@@ skipping 737 matching lines @@
         ['exclude', '^browser/speech/'],
       ],
     }],
     ['linux_use_libgps==1', {
       'dependencies': [
         '../build/linux/system.gyp:libgps',
       ],
     }],
   ],
 }