From agrieve@,
"In addition to diffing a local branch, it might be useful to allow diffing of a committed change...
[no] need to do the build step, as build artifacts for every commit are archived:
See the "zip_build_product" step of chromium.perf builders, example 
https://luci-logdog.appspot.com/v/?s=chrome%2Fbb%2Fchromium.perf%2FAndroid_Builder%2F133430%2F%2B%2Frecipes%2Fsteps%2Fzip_build_product%2F0%2Fstdout
"

-RVG, no need for privacy here.

Just filed  bug 681689 , which is related to the prebuilt comment above. Probably will need to fix that to make this script even nicer.

Also have some more advice after deep-diving on  bug 680973 :
This script should run:
  nm --size-sort --reverse-sort --demangle --synthetic --line-numbers lib.unstripped/libchrome.so | perl -p -e 's/constprop.*?\]/constprop]/g'

on the before and after and show a diff of the two. This is the best way I've found to get insight into what actually changed within the .so file, and doesn't actually take very long to run.

Note: discovered that --line-numbers slows things down quite a bit. Might want to make it optional.

Hmm, lost this one since I failed to label it. Merging as a dupe.