- 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.h
#ifndef ATOM_BROWSER_API_ATOM_API_SESSION_H_
#define ATOM_BROWSER_API_ATOM_API_SESSION_H_
#include <string>
#include "atom/browser/api/trackable_object.h"
#include "atom/browser/atom_blob_reader.h"
#include "base/values.h"
#include "content/public/browser/download_manager.h"
#include "native_mate/handle.h"
#include "net/base/completion_callback.h"
class GURL;
namespace base {
class FilePath;
}
namespace mate {
class Arguments;
class Dictionary;
}
namespace net {
class ProxyConfig;
}
namespace atom {
class AtomBrowserContext;
namespace api {
class Session: public mate::TrackableObject<Session>,