Somewhat difficult bug to describe, easier to show the test case: http://jsfiddle.net/gu7omthf/ Elements in the DOM after the element with css3 transition applied don't appear to respect border-radius + overflow:hidden. Tested in Chrome 39 and Safari 8.0.2, so I surmise that the bug is with WebKit. FF 33 displays the test page correctly.
Safari, Chrome, and Firefox all agree on rendering for this test case. I don't believe there is any remaining compatibility issue.