### Preflight Checklist

* [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:**
  * v10.1.2
* **Operating System:**
  * Windows 10 (1809)
* **Last Known Working Electron version:**
  * 5.0.1  (have not tested others)

### Expected Behavior
From a console, start electron with a remote-debugging-port.  E.g. 

```
$ electron --remote-debugging-port=9092
```

Now navigate to localhost:9092. We would expect to see devtools remotely attached.

### Actual Behavior
A scrambled mess appears. (output is shortened below)
```��Tmo�0��.......```

### To Reproduce
```
$ electron --remote-debugging-port=9092
```

### Additional Information
If you navigate to `http://localhost:9092/json/list`, and then scrape the URL out of `devtoolsFrontendUrl`, you can access them that way. Although this works, it is somewhat of a chore.

shell/browser/ui/devtools_manager_delegate.cc
std::string* name) override {
    return std::unique_ptr<net::ServerSocket>();
  }
  std::string address_;
  uint16_t port_;
  DISALLOW_COPY_AND_ASSIGN(TCPServerSocketFactory);
};
std::unique_ptr<content::DevToolsSocketFactory> CreateSocketFactory() {
  auto& command_line = *base::CommandLine::ForCurrentProcess();
  
  
  int port = 0;
  if (command_line.HasSwitch(switches::kRemoteDebuggingPort)) {
    int temp_port;
    std::string port_str =
        command_line.GetSwitchValueASCII(switches::kRemoteDebuggingPort);
    if (base::StringToInt(port_str, &temp_port) && temp_port >= 0 &&
        temp_port < 65535) {
      port = temp_port;
    } else {
      DLOG(WARNING) << "Invalid http debugger port number " << temp_port;
    }
  }
  return std::unique_ptr<content::DevToolsSocketFactory>(
      new TCPServerSocketFactory("127.0.0.1", port));
}
const char kBrowserCloseMethod[] = "Browser.close";
}  
void DevToolsManagerDelegate::StartHttpHandler() {