v4 - Split button dropdowns get excess width when active on mobile devices

[GeoffYoung]

In the split button dropdowns when the dropdown menu is opened the dropdown-toggle gets some extra width applied.

I'm seeing this on Chrome 44 for android and Safari 8 on iOS

[GeoffYoung]

So there's padding of .375rem 1rem applied to .btn which is causing 16px padding on the left and right.

It's normally being overridden by

.btn-group>.btn+.dropdown-toggle {
    padding-right: 8px;
    padding-left: 8px;
}

but when the dropdown opens <div class="dropdown-backdrop"></div> is created in between that .btn and the .dropdown-toggle, which seems to prevent the sibling selector from applying.

[patrickhlauke]

confirming this for other platforms as well (Android/Chrome, Windows 10 Mobile/Microsoft Edge)

[mdo]

This was addressed with #18807 in Alpha 3. Thanks!