* 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.cc
#include "atom/browser/api/atom_api_menu.h"
#include "atom/browser/native_window.h"
#include "atom/common/native_mate_converters/accelerator_converter.h"
#include "atom/common/native_mate_converters/callback.h"
#include "atom/common/native_mate_converters/image_converter.h"
#include "atom/common/native_mate_converters/string16_converter.h"
#include "native_mate/constructor.h"
#include "native_mate/dictionary.h"
#include "native_mate/object_template_builder.h"
#include "atom/common/node_includes.h"
namespace atom {
namespace api {
Menu::Menu(v8::Isolate* isolate, v8::Local<v8::Object> wrapper)
    : model_(new AtomMenuModel(this)) {
  InitWith(isolate, wrapper);
  model_->AddObserver(this);
}
Menu::~Menu() {
  if (model_) {
    model_->RemoveObserver(this);
  }
}
void Menu::AfterInit(v8::Isolate* isolate) {