How to stop editor removing space ( ) in the beginning of the paragraph

I use WordPress with TinyMCE in Chinese.

It needs double white spaces in the beginning of each paragraph. But the editor will automatically removing all spaces(white space and nbsp; code) in the beginning of the paragraph when I toggle the editor between WYSIWYG mode and HTML mode.

When I used WordPress 3.8, I could stop it doing this with these code

add_filter('tiny_mce_before_init', 'preserve_nbsp_chars');
function preserve_nbsp_chars($initArray) {
    $initArray['entities'] = $initArray['entities'].',160,nbsp';
    return $initArray;
}

The bad thing is it does not work after I updated WP to 4.0.

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