* Output of `node_modules/.bin/electron --version`: v3.0.0-beta.8
* Operating System (Platform and Version): Windows 10 10.0.16299 Build 16299
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): v2.0.8

**Expected Behavior**
Webview DevTools should open in a window that is properly sized.

**Actual behavior**
Webview DevTools open in window with minimal size and are therefore not visible.

**To Reproduce**
**Edit** Works in BrowserWindow.webContents.openDevTools() Works **not** in webView.openDevTools()

**Screenshots**
![too_small_devtools_window](https://user-images.githubusercontent.com/6893212/44841398-850fed80-ac43-11e8-8bed-849d45473683.png)

**Additional Information**
Only reproducible on Windows 10 10.0.16299 Build 16299. Works correctly on MacOS High Sierra 10.13.4

brightray/browser/inspectable_web_contents_impl.cc
const net::CompletionCallback& callback) {
  return net::OK;
}
}  
InspectableWebContentsView* CreateInspectableContentsView(
    InspectableWebContentsImpl* inspectable_web_contents_impl);
void InspectableWebContentsImpl::RegisterPrefs(PrefRegistrySimple* registry) {
  std::unique_ptr<base::DictionaryValue> bounds_dict(new base::DictionaryValue);
  RectToDictionary(gfx::Rect(0, 0, 800, 600), bounds_dict.get());
  registry->RegisterDictionaryPref(kDevToolsBoundsPref, std::move(bounds_dict));
  registry->RegisterDoublePref(kDevToolsZoomPref, 0.);
  registry->RegisterDictionaryPref(kDevToolsPreferences);
}
InspectableWebContentsImpl::InspectableWebContentsImpl(
    content::WebContents* web_contents,
    bool is_guest)
    : frontend_loaded_(false),
      can_dock_(true),
      delegate_(nullptr),
      pref_service_(
          static_cast<BrowserContext*>(web_contents->GetBrowserContext())
              ->prefs()),
      web_contents_(web_contents),