GitLab

Darkening the shelf by 90% for the --ash-shelf-color experiment was too close to
black. Changing to 70% will make the color more visible.

TBR=sky@chromium.org

BUG=595010

Review-Url: https://codereview.chromium.org/2742833006
Cr-Commit-Position: refs/heads/master@{#456183}