The best way to start a File-Drag for now, is the downloadURL as i know.

Like here in Nylas N1:
https://github.com/nylas/N1/blob/master/internal_packages/attachments/lib/attachment-component.cjsx#L67

But only Images and PDFs are able to Drop direct on an Application (MAC). Other file formats just can be copied to Folders.
I think I'm not the only one who is looking for a full native file drop and I think chromium offers that already.

On chrome://downloads/ its possible to Drag any File on an Application (Mac).

Is there maybe a way to access this Drag Function in electron or can it become a part of?
Multi File Drag would be very nice too! :)

[chrome://downloads/ > js dragstart > chrome.send('drag', id)](https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/resources/md_downloads/crisper.js&q=crisper.js&sq=package:chromium&type=cs&l=15751)

I have no knowledge, about cc++ but it found that... :D
[drag_download_item_views.cc](https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/download/drag_download_item_views.cc&q=DragDownloadItem&sq=package:chromium&dr=CSs&l=31)
[md_downloads_dom_handler.cc](https://chromium.googlesource.com/chromium/src.git/+/master/chrome/browser/ui/webui/md_downloads/md_downloads_dom_handler.cc)

atom/browser/api/atom_api_web_contents.cc
v8::Isolate* isolate, const mate::Dictionary& options) {
  auto handle = mate::CreateHandle(isolate, new WebContents(isolate, options));
  g_wrap_web_contents.Run(handle.ToV8());
  return handle;
}
void SetWrapWebContents(const WrapWebContentsCallback& callback) {
  g_wrap_web_contents = callback;
}
}  
}  
namespace {
void Initialize(v8::Local<v8::Object> exports, v8::Local<v8::Value> unused,
                v8::Local<v8::Context> context, void* priv) {
  v8::Isolate* isolate = context->GetIsolate();
  mate::Dictionary dict(isolate, exports);
  dict.SetMethod("create", &atom::api::WebContents::Create);
  dict.SetMethod("_setWrapWebContents", &atom::api::SetWrapWebContents);
  dict.SetMethod("fromId",
                 &mate::TrackableObject<atom::api::WebContents>::FromWeakMapID);
  dict.SetMethod("getAllWebContents",
                 &mate::TrackableObject<atom::api::WebContents>::GetAll);
}
}  
NODE_MODULE_CONTEXT_AWARE_BUILTIN(atom_browser_web_contents, Initialize)