This should reduce the number of merge conflicts when multiple people
touch different generators. There still will be merge conflicts when
two people touch the same code generator.

Bug: angleproject:3691
Change-Id: I0b179368a1352331c091972568c00213ab106e46
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1698650Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Ian Elliott <ianelliott@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>