It appears that in version 1.2.1 that if the animated property is set to true the browser continuously paints the progress bar. Turning this option off ensured resulted in the CPU usage returned to normal.
Animated property simply adds bootstrap's active css class to progress bar. I checked this at bootsrap's docs page and it also is reproduced. So this issue is related with bootstrap's animation of progress bar.
It appears that in version 1.2.1 that if the
animated
property is set totrue
the browser continuously paints the progress bar. Turning this option off ensured resulted in the CPU usage returned to normal.