* 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
return managed_devtools_web_contents_ && view_->IsDevToolsViewShowing();
}
void InspectableWebContentsImpl::AttachTo(
    scoped_refptr<content::DevToolsAgentHost> host) {
  Detach();
  agent_host_ = std::move(host);
  
  
  agent_host_->AttachClient(this);
}
void InspectableWebContentsImpl::Detach() {
  if (agent_host_)
    agent_host_->DetachClient(this);
  agent_host_ = nullptr;
}
void InspectableWebContentsImpl::Reattach(const DispatchCallback& callback) {
  if (agent_host_) {
    agent_host_->DetachClient(this);
    agent_host_->AttachClient(this);
  }
  callback.Run(nullptr);
}
void InspectableWebContentsImpl::CallClientFunction(