History of Engine::tick 2 changes

In crates/backdrop/src/lib.rs, lines 107–134 on 84f09ad45851a6c08d4835e1d3b5a3a9f431af3bc03a107293bdb751d5df7238. Every change that wrote or deleted one of these lines, or deleted a line from between them. Exact, because each line keeps its identity across edits; edits elsewhere in the file are not here. Also: oxy log -L 107,134:crates/backdrop/src/lib.rs.