Try to make transitioning channels actually work. (flutter#14353)

* Try to make transitioning channels actually work.

* Update upgrade.dart

import all generated files in animated_icons_private_test (flutter#14329

)

import all generated files in animated_icons_private_test (flutter#14329

)

Rolling alpha to 0.0.20 (flutter#13511)

Release 0.0.19 (flutter#13365)

Add EdgeInsets, MediaQuery support for view insets (flutter#13272)

* Add MediaQuery support for view insets

Also updates EdgeInsets documentation to reflect WindowPadding's use for
both padding and view insets.

See engine commits:
  flutter/engine#4403
  flutter/engine#4406

release 0.0.17 (flutter#12590)

Version 0.0.16 (flutter#12488)

Release 0.0.15 (flutter#12056)

Roll alpha (flutter#11874)