History of Engine::tick 2 changes

In crates/backdrop/src/lib.rs, lines 107–134 on 73c01b3448ee739021595599fee16f03f873a1ba6a415681d042b7b237569810. 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.