According to the latest specs for CSS Transitions, the timing function code should accept 'ease' and use it as default. See http://webkit.org/specs/CSSVisualEffects/CSSTransitions.html Patch and testcase attached
Created attachment 20644 [details] patch for ease transition
Created attachment 20645 [details] test case for different timing functions
Comment on attachment 20644 [details] patch for ease transition r=me
fixed in r32221