WebAnimations supports infinite iterations. In blink this is simply represented
by std::numeric_limits<double>::infinity() for iterations_count. This seems sensible enough.

However in cc animations we represent infinite iterations by -1 because historically iterations count was represented by an integer. This means trying to map the same time calculation algorithms between blink and cc requires extra mental gymnastic.


CC now uses double for iterations count. So we should use the same value to represent infinity.



[1] https://cs.chromium.org/chromium/src/third_party/blink/renderer/core/animation/compositor_animations.cc?type=cs&sq=package:chromium&g=0&l=550