Testsuite name: JDK Demos manual
Test name(s): tests/demo/jfc/Java2DTest.html
Product(s) tested: JDK 8u231 b01(64bit)
OS/architecture: Ubuntu19.04 x64
option:-Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel -Djdk.gtk.version=3 -Djdk.gtk.verbose=true

Actual results:
1.The Scrollbars displayed incorrectly.Please refer to slider.png
2.we tried to click on the position of the scrollbar, the picture could be changed
3.We tried to maximized the applet,there is the same issue.
4.No such issue without option.Refer to slider-no-option.png