Unit tests for WebStateObserverBridge class.

ios/web/BUILD.gn

Index: ios/web/BUILD.gn
diff --git a/ios/web/BUILD.gn b/ios/web/BUILD.gn
index b4caf9eb0530ad91052d75e5c231d34a1604bcb4..09988d492d9262fbff1cfe6c5f2c1338cbe244c8 100644
--- a/ios/web/BUILD.gn
+++ b/ios/web/BUILD.gn
@@ -381,6 +381,8 @@ source_set("test_support") {
   sources = [
     "public/test/fakes/crw_test_js_injection_receiver.h",
     "public/test/fakes/crw_test_js_injection_receiver.mm",
+    "public/test/fakes/crw_test_web_state_observer.h",
+    "public/test/fakes/crw_test_web_state_observer.mm",
     "public/test/fakes/test_browser_state.cc",
     "public/test/fakes/test_browser_state.h",
     "public/test/fakes/test_java_script_dialog_presenter.h",
@@ -555,6 +557,7 @@ test("ios_web_unittests") {
     "web_state/ui/wk_web_view_configuration_provider_unittest.mm",
     "web_state/web_state_delegate_bridge_unittest.mm",
     "web_state/web_state_impl_unittest.mm",
+    "web_state/web_state_observer_bridge_unittest.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",