* 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
content::WebContents* web_contents,
    content::RenderFrameHost* opener,
    content::SiteInstance* source_site_instance,
    int32_t route_id,
    int32_t main_frame_route_id,
    int32_t main_frame_widget_route_id,
    content::mojom::WindowContainerType window_container_type,
    const GURL& opener_url,
    const std::string& frame_name,
    const GURL& target_url,
    const std::string& partition_id,
    content::SessionStorageNamespace* session_storage_namespace) {
  return false;
}
void InspectableWebContentsImpl::HandleKeyboardEvent(
    content::WebContents* source,
    const content::NativeWebKeyboardEvent& event) {
  auto* delegate = web_contents_->GetDelegate();
  if (delegate)
    delegate->HandleKeyboardEvent(source, event);
}
void InspectableWebContentsImpl::CloseContents(content::WebContents* source) {