Switching back to the new flexbox and re-introducing a scrollable-content node that the flexbox is applied to. This has no height settings so it grows to contains the gutter and lines. The editor outside of it has a width / height of 100% of its container plus overflow-y of scroll. Trying to apply flexbox AND a 100% height + scroll all to the editor causes display artifacts.
For now, I'm removing the flexbox treatment of #app-vertical because the file finder just needs to overlay the bottom and absolute positioning is simpler. I'm also using requireStylesheet to load the file finders CSS instead of a link tag.
