The test suite is ran in 60% of the bots anyway and the
step is very short. For swarming, it's better to run this
together in one step as each step triggers a different bot.

BUG=chromium:535160
LOG=n
NOTRY=true

Review URL: https://codereview.chromium.org/1413023002

Cr-Commit-Position: refs/heads/master@{#31360}