(Feel free to split this into subtasks during sprint)
We would like to get a sense of how reducing HTML size impacts first paint.
We have identified navboxes as representing 10% of the HTML. Although this is minimal compared to reference HTML (see T123328) it provides us a cheap way to verify if reducing HTML does indeed impact the first paint for our users significantly and ensuring we can do a good job of measuring and showing said impact.
 A patch should be prepared that for MobileFrontend (beta only) strips navboxes from the HTML. It should be configurable so we can turn it on and off.
 This should be first deployed on beta cluster in the beta mode channel and we should verify and record there how we expect this to impact first paint, HTML size and server response time
 How does this impact TTFB for the Barack Obama article
 How does this impact First paint for the Barack Obama article
 How does this impact fully load time for the Barack Obama article
 How does this impact HTML bytes for the Barack Obama article
 Now enable on the production cluster and measure the impact on the above as before.
 Patch should now be deployed to the production cluster on enwiki (beta only)
 We should verify and record that the result there matches our expectations on the beta cluster
 Send a report to team detailing lessons learned and how we can improve this implement/measure process in future and what next steps should be (configure off/continue experimentation in this field)
Out of scope:
 Whether we should push this to stable.
 In future we will aim to lazy load the navbox content. We'll deal with this later.