GitLab

Updates Model and RandomTreeTrainer to use TargetDistribution
instead of Model::TargetDistribution.

Change-Id: I0e1a28dc78d5716aa54fd4d1061e86975e4815db
Reviewed-on: https://chromium-review.googlesource.com/c/1352056
Commit-Queue: Frank Liberato <liberato@chromium.org>
Reviewed-by: Fredrik Hubinette <hubbe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611775}