* **Electron Version** (output of `node_modules/.bin/electron --version`):
  * 3.0.6
* **Operating System** (Platform and Version):
  * macOS 10.14

### Expected Behavior
a `new-window` event fires

### Actual behavior
a `did-fail-load` fires with errorCode -3

### To Reproduce
```sh
$ git clone git@github.com:chrismohr/no-new-window.git -b master
$ cd no-new-window/
$ npm i && npm start
```

atom/browser/web_contents_preferences.cc
int process_id) {
  for (WebContentsPreferences* preferences : instances_) {
    content::WebContents* web_contents = preferences->web_contents_;
    if (web_contents->GetMainFrame()->GetProcess()->GetID() == process_id)
      return web_contents;
  }
  return nullptr;
}
WebContentsPreferences* WebContentsPreferences::From(
    content::WebContents* web_contents) {
  if (!web_contents)
    return nullptr;
  return FromWebContents(web_contents);
}
void WebContentsPreferences::AppendCommandLineSwitches(