[bholley]

Yeah, the key reason Rust is necessary here is that there is an insane amount of complexity in the heart of modern web engines. Injecting concurrency into the intersection of DOM and Layout is only realistic with some kind of static guarantees against data races, and Rust is the only tool I'm aware of to do that.

One neat thing is that we use rust-bindgen to walk C++ data structures, which extends Rust's concurrency guarantees into C++. We also have an FFI layer for invoking C++ code, and we have some careful static analysis of that callgraph from the entry points to be sure we're not mutating anything.