Moved |openedByDOM| to WebState's CreateParams and public interface.

ios/web/public/test/fakes/test_web_state_delegate.mm

Index: ios/web/public/test/fakes/test_web_state_delegate.mm
diff --git a/ios/web/public/test/fakes/test_web_state_delegate.mm b/ios/web/public/test/fakes/test_web_state_delegate.mm
index 08fba8d5210e4346a6c066c0cf2bfbc291c29094..dbe1663fef01cc5576002eec2d554e1900fa24db 100644
--- a/ios/web/public/test/fakes/test_web_state_delegate.mm
+++ b/ios/web/public/test/fakes/test_web_state_delegate.mm
@@ -55,9 +55,9 @@
     return nullptr;
   }
 
-  std::unique_ptr<WebStateImpl> child(
-      base::MakeUnique<WebStateImpl>(source->GetBrowserState()));
-  child->GetNavigationManagerImpl().InitializeSession(YES /*opened_by_dom*/);
+  web::WebState::CreateParams params(source->GetBrowserState());
+  params.opened_by_dom = true;
+  std::unique_ptr<web::WebState> child = web::WebState::Create(params);
   child->SetWebUsageEnabled(true);
 
   child_windows_.push_back(std::move(child));