- Electron version: 1.4.3
- Operating system:  @win7
- description:

working on a download app with electron and angular. 
By using webContents.downloadUrl, webContents.session.on('will-download', handler) I can make download function work well, however, I could not find a api to save download progress before closing electron app so that I can restore download when this app is started next time.

Excepted Result:
1. user click 'download' button to download a 1G file.
2. after 500M is downloaded, user quit the app
3. one hour later, user open this app again, and downloading can automatically be restored

atom/browser/api/atom_api_session.cc
browser_context_->prefs()->SetFilePath(
      prefs::kDownloadDefaultDirectory, path);
}
void Session::EnableNetworkEmulation(const mate::Dictionary& options) {
  std::unique_ptr<brightray::DevToolsNetworkConditions> conditions;
  bool offline = false;
  double latency = 0.0, download_throughput = 0.0, upload_throughput = 0.0;
  if (options.Get("offline", &offline) && offline) {
    conditions.reset(new brightray::DevToolsNetworkConditions(offline));
  } else {
    options.Get("latency", &latency);
    options.Get("downloadThroughput", &download_throughput);
    options.Get("uploadThroughput", &upload_throughput);
    conditions.reset(
        new brightray::DevToolsNetworkConditions(false,
                                                 latency,
                                                 download_throughput,
                                                 upload_throughput));
  }
  browser_context_->network_controller_handle()->SetNetworkState(
      devtools_network_emulation_client_id_, std::move(conditions));
  browser_context_->network_delegate()->SetDevToolsNetworkEmulationClientId(
      devtools_network_emulation_client_id_);
}
void Session::DisableNetworkEmulation() {