Summary: The share preference plugin page flashes when INSPECTOR's width is too large. ## Changelog Add 'overflowX: 'hidden'' to FlexRow. Pull Request resolved: https://github.com/facebook/flipper/pull/3903 Test Plan: Pass the test on MAC. Reviewed By: passy Differential Revision: D38784840 Pulled By: mweststrate fbshipit-source-id: 4ca3fc17ccc66767e75ce0f9ab7ad71741dbf15e