Auto merge of #2827 - Turbo87:time-travel, r=locks
Auto merge of #2827 - Turbo87:time-travel, r=locks

tests/helpers: Use time travel instead of time freezing

This ensures that internal timers in the Ember runloop keep ticking correctly instead of being frozen too.

r? `@locks`

rust-lang/crates.io,rust-lang/crates.io,rust-lang/crates.io,rust-lang/crates.io