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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
content::NavigationHandle* navigation_handle) {
  if (navigation_handle->IsInMainFrame() ||
      !navigation_handle->GetURL().SchemeIs("chrome-extension") ||
      !navigation_handle->HasCommitted())
    return;
  content::RenderFrameHost* frame = navigation_handle->GetRenderFrameHost();
  auto origin = navigation_handle->GetURL().GetOrigin().spec();
  auto it = extensions_api_.find(origin);
  if (it == extensions_api_.end())
    return;
  
  
  base::ReplaceFirstSubstringAfterOffset(&it->second, 0, "var chrome",
                                         "var chrome = window.chrome ");
  auto script = base::StringPrintf("%s(\"%s\")", it->second.c_str(),
                                   base::GenerateGUID().c_str());
  
  
  frame->ExecuteJavaScriptForTests(base::UTF8ToUTF16(script),
                                   base::NullCallback());
}
void InspectableWebContents::SendMessageAck(int request_id,
                                            const base::Value* arg) {
  base::Value id_value(request_id);
  CallClientFunction("DevToolsAPI.embedderMessageAck", &id_value, arg, nullptr);
}
}