It would embed array as string instead of joining it like `content_tag` does:

    content_tag(:td, class: ["foo", "bar"]){}
    #=> '<td class="foo bar"></td>'

Before:

    content_tag_for(:td, item, class: ["foo", "bar"]){}
    #=> '<td class="item [&quot;foo&quot;, &quot;bar&quot;]" id="item_1"></td>'

After:

    content_tag_for(:td, item, class: ["foo", "bar"]){}
    #=> '<td class="item foo bar" id="item_1"></td>'