* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test

* Remove uses of deprecated constants
* Change int.parse to int.tryParse where appropriate

The new values are not ready for use yet inside Google

* Roll engine to e976be13c51448f89107d082ec81e2b6731671fa

* move away from deprecated constants

* fix checkLockAcquired: support re-entrant locking

* add test; address comments

* add comment