[markv]

Summary:

Fixes native-driven animations stepping backward for a frame when the shared animated backend is on and a native event update (e.g. an Animated.event onScroll) runs between frames. Without the shared backend this does not happen.

With the shared backend, an event update also steps every active timing, spring and decay animation, at the time of the update. Frames step them at the platform frame time (on Android, the Choreographer vsync time), which is often earlier:

1. An event update steps an animation at time T.
2. The next frame steps it at T - 8..25 ms.
3. The animation moves backward for that frame; a timing animation started by the event overshoots past its start value.

Event updates now only propagate the event values, and time-based animations step only on frames. This aligns the shared backend with the implementations it replaces: the Kotlin NativeAnimatedNodesManager updates nodes on events without stepping animations, and the C++ path without the shared backend steps everything on one clock. As on Kotlin, a timing animation whose toValue tracks an event-driven value restarts on each event and advances only on frames between events.

Changelog: [General][Fixed] - Fix native-driven animations stepping backward when a native event update runs between frames with the shared animated backend

Reviewed By: zeyap

Differential Revision: D127496079

[meta-codesync]

@markv has exported this pull request. If you are a Meta employee, you can view the originating Diff in D127496079.

[react-native-bot]

This pull request was successfully merged by @markv in dee5bb5

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