We should run the OutputPageBeforeHTML hook in VisualEditor API when returning page HTML after editing a page.
Two scenarios came up where that would be helpful:
- MobileFrontend uses the OutputPageBeforeHTML hook to apply mobile-specific transformations to the page (e.g. lead paragraph, collapsible sections). Because of this, VisualEditor currently has to reload the whole page after publishing an edit, instead of using the HTML returned by its API. This makes publishing slower. (T219420)