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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
content::DevToolsAgentHost* agent_host,
    base::span<const uint8_t> message) {
  if (!frontend_loaded_)
    return;
  base::StringPiece str_message(reinterpret_cast<const char*>(message.data()),
                                message.size());
  if (str_message.size() < kMaxMessageChunkSize) {
    std::string param;
    base::EscapeJSONString(str_message, true, &param);
    std::u16string javascript =
        base::UTF8ToUTF16("DevToolsAPI.dispatchMessage(" + param + ");");
    GetDevToolsWebContents()->GetMainFrame()->ExecuteJavaScript(
        javascript, base::NullCallback());
    return;
  }
  base::Value total_size(static_cast<int>(str_message.length()));
  for (size_t pos = 0; pos < str_message.length();
       pos += kMaxMessageChunkSize) {
    base::Value message_value(str_message.substr(pos, kMaxMessageChunkSize));
    CallClientFunction("DevToolsAPI.dispatchMessageChunk", &message_value,
                       pos ? nullptr : &total_size, nullptr);
  }
}
void InspectableWebContents::AgentHostClosed(