User-Agent:       Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
Firefox/52.0
Build Identifier: 

I am using a desktop with multiple harddrives. While coping large files from my
SSD (primary HDD) to a regular spinning HDD (secondary HDD for data) the
notification spinner (part of Event Notification and Actions) displays number
of moving/copying files. While the notification spinner is rotating I observe
that plasmashell process is using over 100% CPU (134% in my case). 

I found an earlier similar issue here -
https://bugs.launchpad.net/ubuntu/+source/plasma-workspace/+bug/1597792

I am on 
KDE Frameworks 5.26.0
Qt 5.6.1 (built against 5.6.1)
The xcb windowing system


Reproducible: Always

Steps to Reproduce:
1. Copy large files between HDD using dolphin
2. Verify that the notification for file copy progress is spinning in system
tray
3. Observe the CPU usage
Actual Results:  
Over 100% of one CPU core is being used for notification

Expected Results:  
File copy progress notification should use very little CPU (may be 1-2%).