### 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
```js
let ret = shell.openItem('file:///noexistent');
console.log(ret);
```
`ret` is always `true` on Linux even if opening fails, e.g.
```sh
xdg-open 'file:///noexistent'
echo $?
```
Shows nonzero error code.

* **Electron Version:**
  * v6.0.11
* **Operating System:**
  *Linux / Ubuntu 16.04 x64

### Expected Behavior
`ret` should be `false`, if `xdg-open` returns non-zero code.

Optional: It would be very nice if the `xdg-open` error (catch stderr) would be displayed in `dialog.showErrorBox` if it returns non-zero code. Just take care that `xdg-open` may write some warnings to stderr even if it returns 0.

shell/common/platform_util_win.cc
if (base::DirectoryExists(full_path))
    return ui::win::OpenFolderViaShell(full_path);
  else
    return ui::win::OpenFileViaShell(full_path);
}
void OpenExternal(const GURL& url,
                  const OpenExternalOptions& options,
                  OpenExternalCallback callback) {
  base::PostTaskAndReplyWithResult(
      base::CreateCOMSTATaskRunner({base::ThreadPool(), base::MayBlock(),
                                    base::TaskPriority::USER_BLOCKING})
          .get(),
      FROM_HERE, base::BindOnce(&OpenExternalOnWorkerThread, url, options),
      std::move(callback));
}
bool MoveItemToTrash(const base::FilePath& path, bool delete_on_fail) {
  base::win::ScopedCOMInitializer com_initializer;
  if (!com_initializer.Succeeded())
    return false;
  Microsoft::WRL::ComPtr<IFileOperation> pfo;
  if (FAILED(::CoCreateInstance(CLSID_FileOperation, nullptr, CLSCTX_ALL,
                                IID_PPV_ARGS(&pfo))))
    return false;
  
  
  if (base::win::GetVersion() >= base::win::Version::WIN8) {
    
    
    if (FAILED(pfo->SetOperationFlags(