- Electron version: 1.2.2
- Operating system: Linux

This is a problem only in linux. It works in OSX.

``` javascript
win.hide()
win.capturePage(function(img){
 // never called
})
```

shell/browser/api/electron_api_web_contents.cc
auto* browser_context = ontents()->GetBrowserContext();
  auto* download_manager =
      content::BrowserContext::GetDownloadManager(browser_context);
  std::unique_ptr<download::DownloadUrlParameters> download_params(
      content::DownloadRequestUtils::CreateDownloadForWebContentsMainFrame(
          ontents(), url, MISSING_TRAFFIC_ANNOTATION));
  download_manager->DownloadUrl(std::move(download_params));
}
GURL WebContents::GetURL() const {
  return ontents()->GetURL();
}
base::string16 WebContents::GetTitle() const {
  return ontents()->GetTitle();
}
bool WebContents::IsLoading() const {
  return ontents()->IsLoading();
}
bool WebContents::IsLoadingMainFrame() const {
  return ontents()->IsLoadingToDifferentDocument();
}
bool WebContents::IsWaitingForResponse() const {
  return ontents()->IsWaitingForResponse();
}
void WebContents::Stop() {
  ontents()->Stop();
}
void WebContents::GoBack() {