Add BookReader.prototype.updateFirstIndex and use instead of setting this.firstIndex directly. Remove some unused variables. Decrease updateNavIndexThrottled time to 250 from 500 to reduce visible changes
Add BookReader.prototype.updateFirstIndex and use instead of setting this.firstIndex directly.
Remove some unused variables.
Decrease updateNavIndexThrottled time to 250 from 500 to reduce visible changes

internetarchive/bookreader,openlibrary/bookreader,openlibrary/bookreader,internetarchive/bookreader,openlibrary/bookreader,openlibrary/bookreader,openlibrary/bookreader