Note that we also change the existing behavior a bit:
CoreService.triggerDataEvent() will not scroll to the bottom unless
`wasUserInput` is also true. This actually seems to be the intended
behavior according to the doc just above
ICoreService.triggerDataEvent().
This change also removes `_currentLinkId` from `InputHandler` and uses
`_curAttrData.extended.urlId` directly so that we don't need to worry
about keep them in sync any more.