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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
const base::Value* found = dict->FindKey("x");
  int x = found ? found->GetInt() : 0;
  found = dict->FindKey("y");
  int y = found ? found->GetInt() : 0;
  found = dict->FindKey("width");
  int width = found ? found->GetInt() : 800;
  found = dict->FindKey("height");
  int height = found ? found->GetInt() : 600;
  return gfx::Rect(x, y, width, height);
}
bool IsPointInRect(const gfx::Point& point, const gfx::Rect& rect) {
  return point.x() > rect.x() && point.x() < (rect.width() + rect.x()) &&
         point.y() > rect.y() && point.y() < (rect.height() + rect.y());
}
bool IsPointInScreen(const gfx::Point& point) {
  for (const auto& display : display::Screen::GetScreen()->GetAllDisplays()) {
    if (IsPointInRect(point, display.bounds()))
      return true;
  }
  return false;
}
void SetZoomLevelForWebContents(content::WebContents* web_contents,
                                double level) {
  content::HostZoomMap::SetZoomLevel(web_contents, level);
}
double GetNextZoomLevel(double level, bool out) {