We currently run a bunch of hooks that embed the "current commit hash" of various repos (src, angle, skia, ...) in the binary.

That's suboptimal for swarming since it means binary hashes change on every commit, even for commits that shouldn't affect the final binary (comment changes, non-source changes to e.g. docs, test-only changes, etc.).


This bug is about trying to stop embedding some or all of these commit hashes.

I know of the following:

- gen/angle/id/commit.h. Says jmadill: "The main use case for the commit.h hashing is to invalidate ANGLE's shader cache on a binary format change. The shader cache is used in Chrome and other ANGLE customers to increase browser & web page load speed. Any change to ANGLE's binary format makes it incompatible with prior versions." Sounds like the shader cache code could instead use a hash of the binary format source code, or a hash of the binary format serialization .a lib.

- src/skia/ext/skia_commit_hash.h. Added in https://chromium.googlesource.com/chromium/src/+/5cacab3ad1c742e08fc26e666171e6b3e4bd99fe ; sounds like it only shows up on chrome://gpu -- could maybe just delete without much ill effects? halcanary?

- GPU_LISTS_VERSION . Also only used on chrome://gpu

- The actual LASTCHANGE file. Mostly embedded in a bunch of .rc files on Windows; also used as "did the last commit change" input in various places.


(I'm not planning to work on this soon; just filing this so I have a list of the things that currently exist.)