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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
extensions::chrome_manifest_urls::GetDevToolsPage(extension.get());
    if (devtools_page_url.is_empty())
      continue;
    
    
    
    content::ChildProcessSecurityPolicy::GetInstance()->GrantRequestOrigin(
        web_contents_->GetMainFrame()->GetProcess()->GetID(),
        url::Origin::Create(extension->url()));
    std::unique_ptr<base::DictionaryValue> extension_info(
        new base::DictionaryValue());
    extension_info->SetString("startPage", devtools_page_url.spec());
    extension_info->SetString("name", extension->name());
    extension_info->SetBoolean("exposeExperimentalAPIs",
                               extension->permissions_data()->HasAPIPermission(
                                   extensions::APIPermission::kExperimental));
    results.Append(std::move(extension_info));
  }
  CallClientFunction("DevToolsAPI.addExtensions", &results, NULL, NULL);
}
#endif
void InspectableWebContents::SetInspectedPageBounds(const gfx::Rect& rect) {
  DevToolsContentsResizingStrategy strategy(rect);
  if (contents_resizing_strategy_.Equals(strategy))
    return;
  contents_resizing_strategy_.CopyFrom(strategy);
  if (managed_devtools_web_contents_)
    view_->SetContentsResizingStrategy(contents_resizing_strategy_);
}
void InspectableWebContents::InspectElementCompleted() {}