Support modifier mouse/scroll action on internal decorated windows
Summary:
This fixes the problem that alt+lmb did not start unrestricted move
resize for the Debug Console.
BUG: 374880
FIXED-IN: 5.12.3
Test Plan: New test case and manual testing whether alt+lmb/rmb works
Subscribers: plasma-devel, kwin
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D10440