<!--  As an open source project with a dedicated but small maintainer team, it can sometimes take a long time for issues to be addressed so please be patient and we will get back to you as soon as we can.
-->

### Preflight Checklist
<!-- Please ensure you've completed the following steps by replacing [ ] with [x]-->

* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.


### 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/api/electron_api_web_contents.cc
bool initially_shown = type_ != Type::kBrowserView;
  options.Get(options::kShow, &initially_shown);
  
  std::string partition;
  gin::Handle<api::Session> session;
  if (options.Get("session", &session) && !session.IsEmpty()) {
  } else if (options.Get("partition", &partition)) {
    session = Session::FromPartition(isolate, partition);
  } else {
    
    session = Session::FromPartition(isolate, "");
  }
  session_.Reset(isolate, session.ToV8());
  std::unique_ptr<content::WebContents> ontents;
  if (IsGuest()) {
    scoped_refptr<content::SiteInstance> site_instance =
        content::SiteInstance::CreateForURL(session->browser_context(),
                                            GURL("chrome-guest:fake-host"));
    content::WebContents::CreateParams params(session->browser_context(),
                                              site_instance);
    guest_delegate_ =
        std::make_unique<WebViewGuestDelegate>(embedder_->ontents(), this);
    params.guest_delegate = guest_delegate_.get();
#if BUILDFLAG(ENABLE_OSR)
    if (embedder_ && embedder_->IsOffScreen()) {
      auto* view = new OffScreenWebContentsView(
          false,