AreaChart:With steps, fmt and labels

Build 300 on references-refactor-and-prop-parity
1200px
Reviewing disabled
Baseline History
Build 30039172e7
Current build. There are unaccepted changes, so build 294 is still the baseline.
Build 2460c9be73
Accepted by Brian D .
Commenting is disabled because there's a newer build on this branch