This commit extracts the storage part of the route-scroll-manager into a dedicated service. This provides a key/value store which will reset for each navigation, and restore previous values when the user uses the back/forward buttons in their browser.
This gives us a reliable replacement for the old `DiscourseRoute.isPoppedState` function, which would not work under all situations.
Previously reverted in e6370decfd. This version has been significantly refactored, and includes an additional system spec for the issue we identified.
This fixes:
- a regression from 30c152c, where navigating to a topic's last reply
via keyboard would lose track of the topic when returning to the topic
list
- an issue where if a topic's last post is a small post, navigating to it
via keyboard would not focus the post
Co-authored-by: David Taylor <david@taylorhq.com>
Using the lastViewedTopicId indiscriminately can cause strange scrolling behavior when navigating to a **different** topic list after viewing a topic. We only want to refocus the topic when going 'back' to the same topic list which originally triggered the navigation.
