Additional timeline info, as I was curious myself. WebP is old enough that a memory safe language was not a feasible option when the project started.
Android 12 was the first version to support Rust code, and came out in 2021 [0, link talks about the first year of integration].
On the iOS side (which also was affected by this), Swift 1.0 came out in ~2014.
As far as I can tell, Chrome doesn't yet support a memory safe language, but do have a bunch of other safety things built in (see MiraclePtr, sandboxing, etc). Since both WebP and Chrome are from Google, this would stop a possible transition.
WebP was announced in 2010, and had its first stable release in 2018 [1].
[0]: https://security.googleblog.com/2022/12/memory-safe-language...
Is Rust in practice a memory safe language when you're doing tricks like decoding huffman-decoding huffman tables into buffers? It seems like once you optimize for performance this much, you're liable to turn off bounds checking here or there.
There are already huffman-decoding and some parts of webp algorithms in https://github.com/google/wuffs (language that finds missing bounds checks during compilations). In contrary, according to readme, this language allows to write more optimized code (compared to C). WEBP decoding is stated as a midterm target in the roadmap.