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### Issue Details
`webContents.openDevTools();` produces error:
`[12703:1102/100312.745262:ERROR:CONSOLE(1)] "Uncaught TypeError: Cannot read property 'setDockSide' of undefined", source: devtools://devtools/bundled/devtools_app.html?remoteBase=https://chrome-devtools-frontend.appspot.com/serve_file/@1eb8474cd7e4fccfbfa8048eceda1eab8b4d394/&can_dock=true&toolbarColor=rgba(223,223,223,1)&textColor=rgba(0,0,0,1)&experiments=true (1)`

Opening dev tools via these methods also produces the same error:
* Right click background > Inspect element
* Ctrl-Shift-I

* **Electron Version:**
  * 11.0.0-beta.18
* **Operating System:**
  * Debian 10 Buster x64, KDE Plasma
* **Last Known Working Electron version:**
  * 10.1.4

### Expected Behavior
Dev tools should open without error.

### Actual Behavior
Above error appears in the terminal.

### To Reproduce
Running this code will probably do it, although I'm opening a URL, but that shouldn't matter.
https://www.electronjs.org/docs/tutorial/quick-start#create-a-basic-application

### Additional Information
I need the beta because the stable version's node is too old.
shell/browser/ui/inspectable_web_contents.cc
if (!success && loader_->NetError() == net::ERR_INSUFFICIENT_RESOURCES &&
        retry_delay_ < kMaxBackoffDelay) {
      const base::TimeDelta delay =
          GetNextExponentialBackoffDelay(retry_delay_);
      LOG(WARNING) << "InspectableWebContents::NetworkResourceLoader id = "
                   << stream_id_
                   << " failed with insufficient resources, retrying in "
                   << delay << "." << std::endl;
      NetworkResourceLoader::Create(
          stream_id_, bindings_, resource_request_, traffic_annotation_,
          std::move(url_loader_factory_), callback_, delay);
    } else {
      base::DictionaryValue response;
      response.SetInteger("statusCode", response_headers_
                                            ? response_headers_->response_code()
                                            : 200);
      auto headers = std::make_unique<base::DictionaryValue>();
      size_t iterator = 0;
      std::string name;
      std::string value;
      while (response_headers_ &&
             response_headers_->EnumerateHeaderLines(&iterator, &name, &value))
        headers->SetString(name, value);
      response.Set("headers", std::move(headers));
      callback_.Run(&response);
    }
    bindings_->loaders_.erase(bindings_->loaders_.find(this));
  }
  void OnRetry(base::OnceClosure start_retry) override {}