This will "help" you "become more familiar with Phabricator's codebase".

This task discusses replacing old callsites with new calls, although much of the work has been done in the intervening time. Here's my best effort at figuring out what's still going on:

• buildStandardPageResponse() looks like it's only present in XHProf and XHPAST. XHProf should be easy to fix, although it may be tricky to test (since you need to install the xhprof PHP extension and configure a bunch of debug stuff). XHPAST may be tricky to fix because it uses weird iframe stuff that doesn't exist anywhere else. If possible, these should be replaced with newPage().
• buildStandardPageView(), same deal.
• buildApplicationPage() appears to have zero remaining callsites. The method can be removed from PhabricatorController.

The SideNavView, ApplicationMenu and PhabricatorApplicationSearchController stuff probably isn't worth fixing in a dedicated way. They still have a ton of callsites, they're more complicated, and they have been getting cleaned up gradually.

Basically, do whatever's easy here and then we can just close it or I can take a stab at fixing the weird iframe stuff. This is just a few simple mechanical fixes that you can use to rack up valuable contributor points as you become more familiar with things.

When converted, all of the new behavior should be exactly identical to the old behavior.

The document Using XHProf may be helpful in testing the XHProf application. Installing XHProf and getting it running will help with doing performance-related work in the future.