PR# 16165 Scrolling inconsistencies in Error List tool

Create a class with about 100 errors. When all errors are displayed in the Error List tool there are two things that do not properly with respect to page by page scrolling.

#1: if you click on the scrollbar below the thumb, it scrolls by slightly more than a page (in my test case, I have 10 + half visible rows, and it scrolls by 12 and slightly more).

#2: if you select the first row and press the page down key, it does the right thing for scrolling, but if you do page up, it scrolls by only half and as a result I have to do twice page up to go back where I was.

I'm not sure if they are grid specific or error list tool specific. I haven't checked the scrolling behavior in other EV_GRIDs of EiffelStudio.