When building chrome, chrome/browser/ui:ui is one of the build targets that need the most time to compile. In my test configuration it needs 78 CPU minutes to compile out of the ~800 CPU minutes currently needed to compile chrome+content_shell+blink_tests with use_jumbo_build=true.
It looks like there is a fair amount of similarly named constants and functions that need to be handled so it's a big fruit but not a low hanging fruit.
Comment 1 by bugdroid1@chromium.org
, Jan 18 2018