### Preflight Checklist

* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details

* **Electron Version:**
  * Tested on electron 5.0.0, through 5.0.6
* **Operating System:**
  * Windows 10 (Tested on both 1803 and 1809)

### Expected Behavior
`process.windowsStore` should return true if running inside of an appx package, as described in https://electronjs.org/docs/api/process#processwindowsstore

### Actual Behavior
`process.windowsStore` returns undefined, even when running in an appx package

### To Reproduce
I forked electron-quick-start to demonstrate the issue I found.
[https://github.com/dangeredwolf/electron-quick-start](https://github.com/dangeredwolf/electron-quick-start)

You can then use `npm run buildWindows` to create the appx.

If you're unfamiliar with appx deployment, appx files need to be signed to be installed, even in developer mode. [This is basically how to do that (from Microsoft's docs)](https://docs.microsoft.com/en-gb/windows/uwp/packaging/sign-app-package-using-signtool)

`process.windowsStore` is undefined in both the main and renderer processes when installed as an AppX

### Screenshots

I set it up to throw a dialog box of whatever process.windowsStore is

![image](https://user-images.githubusercontent.com/2636265/57185775-bb230280-6e9f-11e9-901b-0bb384de9fe8.png)

It's obvious from electron itself that it's running from C:\Program Files\WindowsApps

![image](https://user-images.githubusercontent.com/2636265/57185783-d726a400-6e9f-11e9-8d05-bfc38a959897.png)

### Additional Information

After further testing, I confirmed that this is an issue introduced in Electron 5.0.0. You can test this by cloning [the electron-quick-start fork with process.windowsStore checks](https://github.com/dangeredwolf/electron-quick-start) and changing `package.json`'s `"devDependencies"`>`"electron"` from `"^5.0.0"` to `"^4.2.0"`

![image](https://user-images.githubusercontent.com/2636265/57185900-e9561180-6ea2-11e9-84b7-75a4e3ef7a48.png)
shell/common/application_info_win.cc
if (IsWindows8OrGreater()) {
    
    using GetPackageFamilyNameFuncPtr = decltype(&GetPackageFamilyName);
    static bool initialize_get_package_family_name = true;
    static GetPackageFamilyNameFuncPtr get_package_family_namePtr = NULL;
    if (initialize_get_package_family_name) {
      initialize_get_package_family_name = false;
      HMODULE kernel32_base = GetModuleHandle(L"Kernel32.dll");
      if (!kernel32_base) {
        NOTREACHED() << " " << __FUNCTION__ << "(): Can't open Kernel32.dll";
        return false;
      }
      get_package_family_namePtr =
          reinterpret_cast<GetPackageFamilyNameFuncPtr>(
              GetProcAddress(kernel32_base, "GetPackageFamilyName"));
      if (!get_package_family_namePtr) {
        return false;
      }
    }
    UINT32 length;
    wchar_t packageFamilyName[PACKAGE_FAMILY_NAME_MAX_LENGTH + 1];
    HANDLE proc = GetCurrentProcess();
    LONG result =
        (*get_package_family_namePtr)(proc, &length, packageFamilyName);
    return result == ERROR_SUCCESS;
  } else {
    return false;
  }
}
bool IsRunningInDesktopBridge() {