GitLab

I noticed that md5_check.py was taking up to 200ms for javac actions.
Turns out it was due to it hashing really big .jar files. The utility of
md5_check is that it tracks the md5s of often-changing source files
(e.g. .java files). It's not worth spending >100ms to check if rt.jar has
changed over and over again.

This now uses mtime for files greater than 1mb, and the md5_check
overhead for javac.py is down below 10ms on my machine.

Bug: 906803
Change-Id: I4956419e12b69ad025f12a79d82cf044fc9db34d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1839238Reviewed-by: Sam Maier <smaier@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702859}