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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
bool discover_usb_devices,
    bool port_forwarding_enabled,
    const std::string& port_forwarding_config,
    bool network_discovery_enabled,
    const std::string& network_discovery_config) {}
void InspectableWebContents::SetDevicesUpdatesEnabled(bool enabled) {}
void InspectableWebContents::PerformActionOnRemotePage(
    const std::string& page_id,
    const std::string& action) {}
void InspectableWebContents::OpenRemotePage(const std::string& browser_id,
                                            const std::string& url) {}
void InspectableWebContents::OpenNodeFrontend() {}
void InspectableWebContents::DispatchProtocolMessageFromDevToolsFrontend(
    const std::string& message) {
  
  
  if (base::MatchPattern(message,
                         "{\"id\":*,"
                         "\"method\":\"Page.reload\","
                         "\"params\":*}")) {
    if (delegate_)
      delegate_->DevToolsReloadPage();
    return;
  }
  if (agent_host_)
    agent_host_->DispatchProtocolMessage(
        this, base::as_bytes(base::make_span(message)));
}
void InspectableWebContents::SendJsonRequest(const DispatchCallback& callback,