<!--  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
v8::Local<v8::Value> val,
                     electron::api::WebContents::Type* out) {
    using Type = electron::api::WebContents::Type;
    std::string type;
    if (!ConvertFromV8(isolate, val, &type))
      return false;
    if (type == "backgroundPage") {
      *out = Type::kBackgroundPage;
    } else if (type == "browserView") {
      *out = Type::kBrowserView;
    } else if (type == "webview") {
      *out = Type::kWebView;
#if BUILDFLAG(ENABLE_OSR)
    } else if (type == "offscreen") {
      *out = Type::kOffScreen;
#endif
    } else {
      return false;
    }
    return true;
  }
};
template <>
struct Converter<scoped_refptr<content::DevToolsAgentHost>> {
  static v8::Local<v8::Value> ToV8(