History of Engine::tick 2 changes

In crates/backdrop/src/lib.rs, lines 107–134 on a36c79fd9493ea9a185c484b434b00cfdd7cc2c4d45b9b5b9f0c9f172233791f. 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.