Question on this -- the React.Children approach seems to depend on DocumentCardTitle being the only child that has a title prop, which is problematic since title is also an HTML prop.

So, for instance, this will cause unexpected consequences for the button:

<DocumentCard
    aria-label="Default Document Card with large file name. Created by Annie Lindqvist a few minutes ago."
    onClickHref="http://bing.com"
  >
    <DocumentCardPreview {...previewProps} />
    <DocumentCardTitle title={'File_name.txt'} />
    <button title="tooltip text">Some action</button> 
    <DocumentCardActivity activity="Created a few minutes ago" people={DocumentCardActivityPeople} />
  </DocumentCard>

I think it'd probably be better to implement a context, and have DocumentCardTitle directly pull role/tabindex from it. Some v8 components already do this -- ResizeGroup, ScrollablePane, and ContextualMenu all look like they do, so it wouldn't be unprecedented.

It looks like we'll also need :focus-visible styles for the title, but I'll approve this PR and open a separate issue