[LUCI] increase linux_chromium_headless_rel percentage to 10%

TBR=jbudorick@chromium.org

Bug: 731559
Change-Id: I6ed4bfa7b6c22f41a9fd65732cabc22064eb8162
Reviewed-on: https://chromium-review.googlesource.com/1073620
Reviewed-by: Shenghua Zhang <shenghuazhang@chromium.org>
Commit-Queue: Shenghua Zhang <shenghuazhang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561948}
1 file changed