Is this expected?
Is there some mechanism that would allow an extension to participate in this UX flow and delete their data when the user attempts to clear their browsing history?
Thanks!
Yep, that's the expected behavior. I checked in with devlin@ who called out that there's an extension API that does allow you to clear extension data: chrome.browsingData.remove. Note that the RemovalOptions structure allows you to set originTypes.extension = true. Presumably you could use the backing private API to clear extension data in a "Clear Browsing Data" dialog.
https://developer.chrome.com/extensions/browsingData#type-RemovalOptions
Simeon - @dotproto
Extensions Developer Advocate