Click the down arrow in the News Update section. It stays blue.
This is a regression from 3.2.1, and should be marked as such. Note, resizing the window, or unfocusing then refocusing the window (such as by application switching) causes it to paint correctly.
regressed between r40663 (good) and r40738 (bad)
Created attachment 27706 [details]
reduction, as best as I can get it
<div style="height: 100px; overflow-y: scroll;"><div style="height: 120px;"></div></div>
Created attachment 28430 [details]
Correct the vertical scrollbar rect calculation in RenderLayer::invalidateScrollbarRect()
Fixed in <http://trac.webkit.org/projects/webkit/changeset/41546>.