Eliminates support for Dart 1 in flutter_tools, and drops our Dart 1
benchmarks. All commands now run in Dart 1 mode only.
Eliminates --preview-dart-2 / --no-preview-dart-2 support.
* With dart being default, move preview_dart_2 tests to dart1.
* Swap out defaults for preview-dart-2 option in tests. Make dart1 explicit
* Move suffix around
* Rename files
* Roll engine to b6df7a637498ca9beda1fa9cd7210e3202ea599f.
Changes since last roll:
```
b6df7a637 Roll dart to 290c576264faa096a0b3206c71b2435309d9f904. (#4771)
a6764dbd5 Add sources for Fuchsia target. (#4763)
2d5900615 [fuchsia] Remove unused header file. (#4769)
9717063b7 Revert "Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)" (#4768)
9a9814312 Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)
e74e8b35c [async] Update includes of async headers to new path (#4760)
e2c4b2760 Use Dart 2 camel case constants in the engine Dart libraries (#4766)
9c1e48434 Updates for Fuchsia roll. (#4765)
14c940e27 Switch from fxl::Mutex to std::mutex (#4764)
debf82c0b Roll Garnet (#4759)
5bffdefbb Use weak pointers to the accesibility bridge from objects vended to the UIKit accessibility framework. (#4761)
```
* 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
