Set Parent Width equal to Children Total Width using only CSS?

If you're on Chrome, you can use max-width: fit-content

It's not yet supported by other major browsers though.

UPDATE: As Kasper pointed out in the comments, most browsers now do support max-width: fit-content (albeit with a vendor prefix in the case of Firefox)

I know this is a bit late, but Hope this will help somebody who is looking for similar solution:

<div class="parent" style="display: inline-flex">
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
        </div>

the trick is to use inline-flex for the parent and inline-table for the child. Everything is dynamic. I make the table scrollable horizontally by adding another grandparent with overflow-x:scroll;:

<div class="grandparent" style="width: 300px; overflow-x: scroll; background: gray">
        <div class="parent" style="display: inline-flex">
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
            <div class="child" style="display: inline-table">some button</div>
        </div>
    </div>