Fix fast scrolling with Shift+Scroll

When holding down the shift key, multiply wheel and touchpad scroll
distances by 10 to re-implement the fast scrolling feature that
broke when we added animated/smooth scrolling.

BUG: 420889
FIXED-IN: 1.11.3
5 jobs for !298 with release/20.08 in 54 minutes and 23 seconds (queued for 476 minutes and 29 seconds)
detached
Status Job ID Name Coverage
  Build
passed #73806
build_clazy_clang_tidy

00:16:23

passed #73804
build_ubuntu_18_04

00:10:09

passed #73805
build_ubuntu_20_04

00:13:35

passed #73807
clang_format

00:01:19

passed #73803
linux kf5-qt5 qt5.12

00:12:55

44.0%