* It's time to #deleteDart1 (#18293)
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.
* Fix indentation, remove no longer necessary .toList()
* Only push udpated kernel if >0 invalidated srcs
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.
* Allow FloatingActionButton to not have a heroTag.
* Allow FloatingActionButton to not have a child.
* Allow Tooltip to not have a child.
* Improve the debug output of the default FloatingActionButton hero tag.
* Improve the error message in the Hero clashing-tag case.
* Improve the debug output of the Hero widget.
* Improve the debug output of gesture-related widgets.
* Minor improvements to documentation.
* Fix some typos in comments.
* Fix some style nits.