BaseTabs:Breaking out of container margin

Build 1240 on dzucconi/chore/storybook-upgrade
1200px
Reviewing disabled
The baseline is wider than the new snapshot (1200x38 to 1168x38).
Baseline History
Build 1240864b19e
Current build. There are unaccepted changes, so build 1143 is still the baseline.
Commenting is disabled because there's a newer build on this branch