Summary: Pull Request resolved: https://github.com/facebook/yoga/pull/1646 X-link: https://github.com/facebook/react-native/pull/44069 Fixes https://github.com/facebook/yoga/issues/978 1. Don't allow auto margin spaces to become a negative length 2. Replicate fallback alignment behavior specified by box-alignment spec that we are using for align-content. Reviewed By: joevilches Differential Revision: D56091577 fbshipit-source-id: 3c02f81f969bb947cdc5c80b15faaa0b0d39c0c2