* 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
private:
  void InsertItemAt(int index, int command_id, const base::string16& label);
  void InsertSeparatorAt(int index);
  void InsertCheckItemAt(int index,
                         int command_id,
                         const base::string16& label);
  void InsertRadioItemAt(int index,
                         int command_id,
                         const base::string16& label,
                         int group_id);
  void InsertSubMenuAt(int index,
                       int command_id,
                       const base::string16& label,
                       Menu* menu);
  void SetIcon(int index, const gfx::Image& image);
  void SetSublabel(int index, const base::string16& sublabel);
  void SetRole(int index, const base::string16& role);
  void Clear();
  int GetIndexOfCommandId(int command_id);
  int GetItemCount() const;
  int GetCommandIdAt(int index) const;
  base::string16 GetLabelAt(int index) const;
  base::string16 GetSublabelAt(int index) const;
  bool IsItemCheckedAt(int index) const;
  bool IsEnabledAt(int index) const;
  bool IsVisibleAt(int index) const;
  
  base::Callback<bool(v8::Local<v8::Value>, int)> is_checked_;
  base::Callback<bool(v8::Local<v8::Value>, int)> is_enabled_;
  base::Callback<bool(v8::Local<v8::Value>, int)> is_visible_;