BS3: Difficult (impossible?) to see if an btn-default is active or not

[pmorch]

It isn't easy to see if a bnt-default based checkbox is active or not.

To illustrate, lets look at three right next to each other. If they are either all active or all not-active, it isn't easy to see whether they're all active or not. It helps if at least one is in a different state.

I've modified the Javascript Checkbox Button Example to create this jsFiddle demonstrating the issue, but here are some screen shots too.

Imagine arriving at a page and seeing the top image. Are all these checkboxes checked or not?

A single stand-alone btn-default checkbox also has this issue.

E.g. btn-primary-s also have this to some extent, but to my non-designer eye, it looks more pronounced with btn-default.

[cvrebert]

Related: #8786

[mdo]

Closing as a dupe then. I'll look into it fur sure.