x11-misc/lightdm-kde has not seen any development since 2013 and consequently still rdepends on kde-apps/plasma-runtime, which in turn blocks dev-qt/qtwebkit:4 removal.
CCing hwoarang since x11-misc/lightdm[kde] would need to be dropped.
Author: Michał Górny <firstname.lastname@example.org>
AuthorDate: Wed Jul 5 11:52:09 2017
Commit: Michał Górny <email@example.com>
CommitDate: Wed Jul 5 12:00:08 2017
x11-misc/lightdm-kde: Remove last-rited pkg, #620796