See attached example, click the "Click here" label. The red ball is moved but about half of it is still shown on the previous position. Repeated also in Google Chrome.
Created attachment 25752 [details] Sample file. Click the "click here" to see the bug, refresh page to repeat
Created attachment 25816 [details] First attempt Here is my fix for this problem. I am afraid a pixel test is needed to really expose this bug. Cheers, Rob.
Mitz or Hyatt could better tell if this is right.
Comment on attachment 25816 [details] First attempt r=me
Landed in r39574.