[ios] Added web// public API to let embedder observe loading progress.

ios/web/ios_web_unittests.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': [
     {
       # GN version: //ios/web:ios_web_unittests
@@ skipping 50 matching lines @@
         'web_state/js/crw_js_window_id_manager_unittest.mm',
         'web_state/js/page_script_util_unittest.mm',
         'web_state/ui/crw_web_controller_container_view_unittest.mm',
         'web_state/ui/crw_web_controller_observer_unittest.mm',
         'web_state/ui/crw_web_controller_unittest.mm',
         'web_state/ui/crw_wk_script_message_router_unittest.mm',
         'web_state/ui/web_view_js_utils_unittest.mm',
         'web_state/ui/wk_back_forward_list_item_holder_unittest.mm',
         'web_state/ui/wk_web_view_configuration_provider_unittest.mm',
         'web_state/web_state_impl_unittest.mm',
+        'web_state/web_state_delegate_bridge_unittest.mm',
+        "web_state/web_state_delegate_stub.h",
+        "web_state/web_state_delegate_stub.mm",
         'web_state/web_view_internal_creation_util_unittest.mm',
         'web_state/wk_web_view_security_util_unittest.mm',
         'webui/crw_web_ui_manager_unittest.mm',
         'webui/crw_web_ui_page_builder_unittest.mm',
         'webui/url_fetcher_block_adapter_unittest.mm',
       ],
       'actions': [
         {
           'action_name': 'copy_test_data',
           'variables': {
             'test_data_files': [
               '../../net/data/ssl/certificates/',
               'test/data/chrome.html',
               'test/data/testbadpass.pkpass',
               'test/data/testfavicon.png',
               'test/data/testpass.pkpass',
             ],
             'test_data_prefix': 'ios/web',
           },
           'includes': [ '../../build/copy_test_data_ios.gypi' ],
         },
       ],
     },
   ],
 }