Avoid duplicate markdown sanitization

[DonJayamanne]

For #210528

[DonJayamanne]

Only changed the order of the attributes, else the HTML is identical

[mjbvz]

Also would like to get a repo. In my testing of the linked issue, the call to sanitize takes under 1ms. Even if we don't call sanitize twice, it sounds like we'd still be taking 150ms or so which isn't acceptable

[DonJayamanne]

n my testing of the linked issue, the call to sanitize takes under 1ms. Even if we don't call sanitize twice, it sounds like we'd still be taking 150ms or so which isn't acceptable

Sometimes I have seen this taking 300ms when working on notebooks, we use markdown parser to build outlines and that ends up parsing markdown which results in 300ms sometimes.
So, this is definitely happening in other places too, but not 100% of the time.
The issue does definitely repro for me, please let me know if CPU profiles will help and what else information you need.