* Electron version: 1.4.15
* Operating system: Windows 10

### Expected behavior

The new [before-input-event](https://github.com/electron/electron/blob/master/docs/api/web-contents.md#event-before-input-event) event should imitate the properties from [KeyboardEvents](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent).

### Actual behavior

Missing the ```KeyboardEvent.code``` equivalent.
Because of this, it's not possible for me to distinguish between my shortcuts created with 1 and Numpad1 for instance.

Looking at comments for the ```before-input-event``` issue ([#7586](https://github.com/electron/electron/issues/7586#issuecomment-263431783)), The ```code``` property was never mentioned in the psudo code. Missed by mistake?

```code``` is available on the ```keydown``` events in Electron, which I use now. I'm not able to rewrite my code to use ```before-input-event```, for now.
atom/common/native_mate_converters/blink_converter.cc
mate::Dictionary dict = mate::Dictionary::CreateEmpty(isolate);
  dict.Set("canUndo",
      !!(editFlags & blink::WebContextMenuData::CanUndo));
  dict.Set("canRedo",
      !!(editFlags & blink::WebContextMenuData::CanRedo));
  dict.Set("canCut",
      !!(editFlags & blink::WebContextMenuData::CanCut));
  dict.Set("canCopy",
      !!(editFlags & blink::WebContextMenuData::CanCopy));
  bool pasteFlag = false;
  if (editFlags & blink::WebContextMenuData::CanPaste) {
    std::vector<base::string16> types;
    bool ignore;
    ui::Clipboard::GetForCurrentThread()->ReadAvailableTypes(
        ui::CLIPBOARD_TYPE_COPY_PASTE, &types, &ignore);
    pasteFlag = !types.empty();
  }
  dict.Set("canPaste", pasteFlag);
  dict.Set("canDelete",
      !!(editFlags & blink::WebContextMenuData::CanDelete));
  dict.Set("canSelectAll",
      !!(editFlags & blink::WebContextMenuData::CanSelectAll));
  return mate::ConvertToV8(isolate, dict);
}
v8::Local<v8::Value> MediaFlagsToV8(v8::Isolate* isolate, int mediaFlags) {