When editing, no option to add a code snippet

When editing an existing test, there does not appear to be an interface element to "add" a new code snippet like there is when creating a new test.

Expected behavior: when editing a test such as //jsperf.com/transpose-2d-array/5/edit
there should be a button at the bottom of the code snippets section to "Add code snippet".

PS, I am on Chrome 54 Win 10.
