Flutter web at 120 Hz on Android

Chrome on Android holds a page's own animation to 60 frames per second on 120 Hz screens, so Flutter web apps scroll and animate at 60. flutter_shim.js moves Flutter's frame clock and canvas to a worker, which Chrome doesn't limit.

Each example below runs from one build, twice: Before as it ships, After with the shim. The badge in the corner shows frames per second; tap it to switch versions on the same screen.