* Electron version: 1.8.2-beta.3
* Operating system: MacOS 10.12

### Expected behavior

File downloads from custom protocols should complete without issue.

### Actual behavior

Before even triggering the custom protocol handler, the download-item emits 'done' with a state of 'interrupted'. In my demo linked below, I use the new registerStreamProtocol, but I was able to reproduce using registerHttpProtocol as well.

### How to reproduce

Use https://github.com/pfrazee/electron-download-interrupt-bug

atom/browser/api/atom_api_protocol.h
return weak_factory_.GetWeakPtr();
  }
  scoped_refptr<brightray::URLRequestContextGetter> request_context_getter_;
  base::WeakPtrFactory<Protocol> weak_factory_;
  DISALLOW_COPY_AND_ASSIGN(Protocol);
};
}  
}  
#endif