* Electron version: 1.7.x
* Operating system: Windows

### Expected behavior
removeAsDefaultProtocolClient should also delete the protocol key - HKCU\Software\Classes\#protocol#

### Actual behavior
removeAsDefaultProtocolClient doesn't delete the protocol key - HKCU\Software\Classes\#protocol#

### How to reproduce
Call app.setAsDefaultProtocolClient('foo') and app.removeAsDefaultProtocolClient('foo'). HKCU\Software\Classes\foo stay in the registry for windows.
atom/browser/browser_win.cc
DWORD target_process_id = *reinterpret_cast<DWORD*>(param);
  DWORD process_id = 0;
  GetWindowThreadProcessId(hwnd, &process_id);
  if (process_id == target_process_id) {
    SetFocus(hwnd);
    return FALSE;
  }
  return TRUE;
}
bool GetProcessExecPath(base::string16* exe) {