element.addClass('dropdown-toggle'); line breaks dropdown focus

[Codermar]

Line 311 on dropdown.js breaks accessibility dropdown focus in button.

element.addClass('dropdown-toggle');

Removing it resolves it.

Please attach to #4772

[wesleycho]

Why would this break focus? Can you explain in more detail/post a reproduction in Plunker?

[Codermar]

Not a bug, my apologies, the cause of this is the override in the bootstrap css:
.dropdown-toggle:focus {
outline: 0;
}
I am not sure why they decided to remove the outline. My accessibility QA raised this issue so I've restored the outline:
.dropdown-toggle:focus {
outline: auto 5px -webkit-focus-ring-color;
}