* Change some of the dev/devicelab tests to support testing against local engine.
We can already configure flutter tools to use local engine by setting
FLUTTER_ENGINE environment variable. However when this variable is set
this also requires setting --local-engine to specify which flavor of
engine to use.
This change changes tests in dev/devicelab to pass a sensible default for
--local-engine, e.g. when testing hot reload on Android we pass android_debug
and when testing release AOT build for IOS we pass ios_release.
* Fix analysis issues
* Update utils.dart
* Restructure hot mode test so it runs interactively.
This allows to add a benchmark for hot reload after actual source code change.
* Add curly braces, refactory copyRecursive
* Add hotReloadInitialDevFSSyncMilliseconds to track how long user have to wait before being able to do first reload.
This stat is significantly different between existing and preview-dart-2 setting (for the latter, this stat is ~3x slower: 13s vs ~4s).
* Remove ws
* Cleanup timer-related code
* Clone hot reload benchmark for --preview-dart-2 option.
* Get rid of linux and win preview_dart_2 (only android would be sufficient for now). Refactor code into lib/tasks
* Revert 2016 to 2017
* Mark new test as flaky
