GitLab

We are in the process of migrating to R8 to replace Proguard. This is
the first step - move all usages of Proguard in public targets to R8.

Some refactorings were natural with the few forced changes this caused.

TBR=smaier

Bug: 908988, 913554
Change-Id: I2139919598fba1643d7560dc5557d5efb9a5887c
Reviewed-on: https://chromium-review.googlesource.com/c/1357306Reviewed-by: Sam Maier <smaier@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Sam Maier <smaier@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619471}