* Output of `node_modules/.bin/electron --version`: v3.0.6
* Operating System (Platform and Version): Windows 10 (October Update)

**Expected Behavior**
When using the accelerator "Shift+Backspace" in a `Menu`, the accelerator should be displayed as "Shift+Backspace"

**Actual behavior**
"Shift+Shift+Backspace" is displayed as accelerator in the menu.

**To Reproduce**
See: https://github.com/torjusb/electron-accelerator-bug

**Screenshots**
<img width="385" alt="accelerator" src="https://user-images.githubusercontent.com/53583/47494149-49635f80-d851-11e8-8178-eed38f22e0e2.png">

**Additional info**
This only appears to affect "Shift+Backspace" from limited testing. Accelerators such as "Alt+Backspace", "Shift+M" etc. appears to work fine.
atom/browser/api/atom_api_menu.h
base::Callback<v8::Local<v8::Value>(v8::Local<v8::Value>, int, bool)>
      get_accelerator_;
  base::Callback<void(v8::Local<v8::Value>, v8::Local<v8::Value>, int)>
      execute_command_;
  base::Callback<void(v8::Local<v8::Value>)> menu_will_show_;
  DISALLOW_COPY_AND_ASSIGN(Menu);
};
}  
}  
namespace mate {
template <>
struct Converter<atom::AtomMenuModel*> {
  static bool FromV8(v8::Isolate* isolate,
                     v8::Local<v8::Value> val,
                     atom::AtomMenuModel** out) {
    
    if (val->IsNull()) {
      *out = nullptr;
      return true;
    }
    atom::api::Menu* menu;
    if (!Converter<atom::api::Menu*>::FromV8(isolate, val, &menu))
      return false;
    *out = menu->model();
    return true;
  }
};
}  
#endif