Revert "Update D8 and R8 to 1.5.18-dev"

This reverts commit 224276328a804f422710ac7f481d1ebfe3fec67d.

Reason for revert: cf_x86_phone-userdebug (linux) build 5469465 in git_master is broken

Change-Id: Ic65fb32f399fd104ddaf1975d765879f2f6126df
6 files changed