* 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
protected:
  Menu(v8::Isolate* isolate, v8::Local<v8::Object> wrapper);
  ~Menu() override;
  
  void AfterInit(v8::Isolate* isolate) override;
  
  bool IsCommandIdChecked(int command_id) const override;
  bool IsCommandIdEnabled(int command_id) const override;
  bool IsCommandIdVisible(int command_id) const override;
  bool GetAcceleratorForCommandIdWithParams(
      int command_id,
      bool use_default_accelerator,
      ui::Accelerator* accelerator) const override;
  void ExecuteCommand(int command_id, int event_flags) override;
  void MenuWillShow(ui::SimpleMenuModel* source) override;
  virtual void PopupAt(TopLevelWindow* window,
                       int x,
                       int y,
                       int positioning_item,
                       const base::Closure& callback) = 0;
  virtual void ClosePopupAt(int32_t window_id) = 0;
  std::unique_ptr<AtomMenuModel> model_;
  Menu* parent_ = nullptr;
  
  void OnMenuWillClose() override;
  void OnMenuWillShow() override;