Notify SystemURLRequestContextGetter before shutdown on iOS.

ios/chrome/BUILD.gn

Index: ios/chrome/BUILD.gn
diff --git a/ios/chrome/BUILD.gn b/ios/chrome/BUILD.gn
index 73ab352cb70f1ccf48f72af4abdaf21987f66f4e..7545222d8d2013428e5126b639fa5cad09aef4f3 100644
--- a/ios/chrome/BUILD.gn
+++ b/ios/chrome/BUILD.gn
@@ -41,6 +41,7 @@ test("ios_chrome_unittests") {
     "browser/geolocation/omnibox_geolocation_local_state_unittest.mm",
     "browser/install_time_util_unittest.mm",
     "browser/installation_notifier_unittest.mm",
+    "browser/ios_chrome_io_thread_unittest.mm",
     "browser/itunes_links/itunes_links_observer_unittest.mm",
     "browser/metrics/ios_chrome_metrics_service_accessor_unittest.cc",
     "browser/metrics/ios_chrome_stability_metrics_provider_unittest.cc",
@@ -99,8 +100,10 @@ test("ios_chrome_unittests") {
     "//components/password_manager/core/browser:test_support",
     "//components/password_manager/core/common",
     "//components/prefs:test_support",
+    "//components/proxy_config:proxy_config",
     "//components/signin/core/browser:test_support",
     "//components/signin/ios/browser:test_support",
+    "//components/ssl_config:ssl_config",
     "//components/sync_driver:test_support",
     "//components/syncable_prefs:test_support",
     "//components/update_client",