In order for the animation code to be aligned in terms of features between animations running entirely by modifying RenderStyle ("software" animations) and animations running by modifying CALayer properties ("accelerated animations), we should run accelerated animations in a separate thread using the same blending code used for software animations and stop relying on Core Animation to perform the animations.
rdar://100595691
The expected benefits of this work will be that the following animation types that weren't accelerated will now benefit from acceleration: - CSS Motion Path properties (`offset` et al) - additive and accumulating composition - steps() timing function - cubic-bezier() timing functions with values outside of the 0-1 range - playbackRate != 1 And going forward this will also mean that adding features to our Web Animations codebase will benefit all types of animations, both software and accelerated, with minimal effort. We should also be able to have better control over the timing at which animation frames are resolved and address some sync issues between software and accelerated animations.