This reverts commit 41b50c22.

Started handling messages from background isolates.

* Introduce tests for tristate checkboxes

* Initial

* Use tristate changes in engine

* Flutter_test matchers test update

* Comments, tests

* Update packages/flutter/lib/src/semantics/semantics.dart
Co-authored-by: Chris Bracken <chris@bracken.jp>

* Assert mutual exclusivity

* Assert valid state before updating state

* Update packages/flutter/lib/src/semantics/semantics.dart

Typo fix in comment
Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>
Co-authored-by: Chris Bracken <chris@bracken.jp>
Co-authored-by: Loïc Sharma <737941+loic-sharma@users.noreply.github.com>

This reverts commit f477c8b1.

* Introduce stubbed `exclusive` parameter to `File.create`-overridden method.

This is to soften landing of a breaking change https://github.com/dart-lang/sdk/issues/49647

This reverts commit ff9fe356.

In particular, to get `material_color_utilities` `0.2.0`.

Explain the "patching" protocol in `KeyMessageManager.keyMessageHandler` and add an example (#105280)

This reverts commit 641f4e24.

* Revert "Reland "Clipping if only one character text overflows (#99146)" (#102130)"

This reverts commit 3f43d9f3.

* Revert "Implement frameData for TestWindow (#105537)"

This reverts commit 21841d7e.