* 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::URLFetcher* source) {
  DCHECK(source);
  auto it = pending_requests_.find(source);
  DCHECK(it != pending_requests_.end());
  base::DictionaryValue response;
  net::HttpResponseHeaders* rh = source->GetResponseHeaders();
  response.SetInteger("statusCode", rh ? rh->response_code() : 200);
  {
    auto headers = std::make_unique<base::DictionaryValue>();
    size_t iterator = 0;
    std::string name;
    std::string value;
    while (rh && rh->EnumerateHeaderLines(&iterator, &name, &value))
      headers->SetString(name, value);
    response.Set("headers", std::move(headers));
  }
  it->second.Run(&response);
  pending_requests_.erase(it);
  delete source;
}
void InspectableWebContentsImpl::SendMessageAck(int request_id,
                                                const base::Value* arg) {
  base::Value id_value(request_id);
  CallClientFunction("DevToolsAPI.embedderMessageAck", &id_value, arg, nullptr);
}
}