* 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
bool docked) {
  if (managed_devtools_web_contents_)
    view_->SetIsDocked(docked);
  if (!callback.is_null())
    callback.Run(nullptr);
}
void InspectableWebContentsImpl::OpenInNewTab(const std::string& url) {}
void InspectableWebContentsImpl::ShowItemInFolder(
    const std::string& file_system_path) {
  if (file_system_path.empty())
    return;
  base::FilePath path = base::FilePath::FromUTF8Unsafe(file_system_path);
  platform_util::ShowItemInFolder(path);
}
void InspectableWebContentsImpl::SaveToFile(const std::string& url,
                                            const std::string& content,
                                            bool save_as) {
  if (delegate_)
    delegate_->DevToolsSaveToFile(url, content, save_as);
}
void InspectableWebContentsImpl::AppendToFile(const std::string& url,