- 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
v8::Local<v8::FunctionTemplate> prototype) {
  prototype->SetClassName(mate::StringToV8(isolate, "Session"));
  mate::ObjectTemplateBuilder(isolate, prototype->PrototypeTemplate())
      .MakeDestroyable()
      .SetMethod("resolveProxy", &Session::ResolveProxy)
      .SetMethod("getCacheSize", &Session::DoCacheAction<CacheAction::STATS>)
      .SetMethod("clearCache", &Session::DoCacheAction<CacheAction::CLEAR>)
      .SetMethod("clearStorageData", &Session::ClearStorageData)
      .SetMethod("flushStorageData", &Session::FlushStorageData)
      .SetMethod("setProxy", &Session::SetProxy)
      .SetMethod("setDownloadPath", &Session::SetDownloadPath)
      .SetMethod("enableNetworkEmulation", &Session::EnableNetworkEmulation)
      .SetMethod("disableNetworkEmulation", &Session::DisableNetworkEmulation)
      .SetMethod("setCertificateVerifyProc", &Session::SetCertVerifyProc)
      .SetMethod("setPermissionRequestHandler",
                 &Session::SetPermissionRequestHandler)
      .SetMethod("clearHostResolverCache", &Session::ClearHostResolverCache)
      .SetMethod("allowNTLMCredentialsForDomains",
                 &Session::AllowNTLMCredentialsForDomains)
      .SetMethod("setUserAgent", &Session::SetUserAgent)
      .SetMethod("getUserAgent", &Session::GetUserAgent)