Update fontconfig cache key handling

Since If6853404f1e87de4f95a24f6231282543814bd63, the "uuid" variable has
been referring to the MD5 of a fixed string. Update the comment as such,
and remove the now-unneeded .uuid file writing.

Also update test_fonts/README.chromium as the manual UUID change is no
longer necessary or effective.

Bug: 767754
Change-Id: I07a9b10a631e755877cbcb7df40a53359329f8a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2209397
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Auto-Submit: Timothy Gu <timothygu@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770287}
GitOrigin-RevId: eb686109386934e0ced433a64f1e6704afc613ab
1 file changed