3938: wrong interdiff displayed when rapidly dragging to a specific change

bjoern.*******@deze**** (Google Code) (Is this you? Claim this profile.)
What version are you running?

What's the URL of the page containing the problem?

What steps will reproduce the problem?
1. have a review that contains multiple diffs
2. move one of the sliders to a different revision
3. before the changes between the revisions are loaded, move the other slider to yet another revision

What is the expected output? What do you see instead?
It is expected see the diff between the selected revisions.
Actually displayed is the diff between the revisions that were selected before moving the second slider.

What operating system are you using? What browser?
Kubuntu 14.04,  Firefox 39

Please provide any additional information below.
See the attached image. Revisions 13-14 are supposedly displayed (as implied in the url), but if a review is created it is for revisions 13-30.