CSS Gradients can cause a significant slowdown in rendering performance when using CSS Transitions, but this is predominantly noticeable on the MacBook Air and other computers with integrated graphics.
Moving an element around that sits on top of a gradient causes serious frame rate drops (as measured with Quartz Debug). On a solid background it transitions smoothly.
Created attachment 29108 [details]
Reduced test case
Created attachment 29109 [details]
Test case showing that giving the HTML element a background color fixes the issue
Added a second test case that sets a solid color on the html element, which makes performance snappy again. Using a gradient (third test case, soon to be attached) as opposed to a solid color, makes it go slow again.
Created attachment 29110 [details]
Third test case, using a gradient on the HTML element
Same cause as bug 24130.
*** This bug has been marked as a duplicate of 24130 ***