Follow-up with Collapsible header issues

Collapsible headers should work without any quirks or glitches. In particular, look out for the following scenarios: Course home: header should collapse/expand on scroll. Long activity: header should collapse/expand on scroll. Short activity (an activity with scroll, but not enough to collapse header completely): header should not collapse at all (shouldn't behave like a collapsible header). Activity without scroll: header should not collapse at all (shouldn't behave like a collapsible header). Changing tabs in the course home should keep header working; and changing tabs will reset the header to be fully expanded. Calendar events (most of them are too short, but if you find one that is long enough it should behave like activities). Going back and forth between pages with collapsible headers shouldn't cause any visual glitches. Try these in both mobile and tablet layouts.