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### Issue Details
Electron Version: All Version
Operating System: macOS 10.15.3
Last Known Working Electron version: Never

### Bug
The color picker in devtools does not work.
In devtools if you want to change the colors of the CSS code. When you click on a color a color picker is supposed to appear but it does not appear.

### Screenshots
<img width="1013" alt="Capture d’écran 2020-09-07 à 11 42 44" src="https://user-images.githubusercontent.com/70572698/92374841-988ea280-f100-11ea-96be-afc93f6dd645.png">

shell/browser/ui/inspectable_web_contents.cc
GetDevToolsWebContents()->DispatchBeforeUnload(false );
}
void InspectableWebContents::LoadCompleted() {
  frontend_loaded_ = true;
  if (managed_devtools_web_contents_)
    view_->ShowDevTools(activate_);
  
  if (!can_dock_) {
    SetIsDocked(DispatchCallback(), false);
  } else {
    if (dock_state_.empty()) {
      const base::DictionaryValue* prefs =
          pref_service_->GetDictionary(kDevToolsPreferences);
      std::string current_dock_state;
      prefs->GetString("currentDockState", &current_dock_state);
      base::RemoveChars(current_dock_state, "\"", &dock_state_);
    }
    std::u16string javascript = base::UTF8ToUTF16(
        "UI.DockController.instance().setDockSide(\"" + dock_state_ + "\");");
    GetDevToolsWebContents()->GetMainFrame()->ExecuteJavaScript(
        javascript, base::NullCallback());
  }
#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
  AddDevToolsExtensionsToClient();
#endif
  if (view_->GetDelegate())
    view_->GetDelegate()->DevToolsOpened();
}
#if BUILDFLAG(ENABLE_ELECTRON_EXTENSIONS)
void InspectableWebContents::AddDevToolsExtensionsToClient() {