This reverts commit 14552a96.

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

This adds a FocusableActionDetector, a widget which combines the functionality of Actions, Shortcuts, MouseRegion and a Focus widget to create a detector that defines actions and key bindings, and will notify that the focus or hover highlights should be shown or not. This widget can be used to give a control the required detection modes for focus and hover handling on desktop and web platforms.

I replaced a bunch of similar code in many of our widgets with this widget, and found that pretty much any control that wants to be focusable wants all of these features as well: focus highlights, hover highlights, and actions to activate it.

Also eliminated an extra _hasFocus variable in FocusState that wasn't being used.

This re-lands the change that adds focus nodes, hover, and shortcuts to switches, checkboxes, and radio buttons. (#43213), with fixes for the web tests that weren't enabled in the master that it was synced to when I first landed it.

Revert "Re-Land: Add focus nodes, hover, and shortcuts to switches, checkboxes, and radio buttons. (#43384)" (#43647)

This reverts commit 8017f63b, since it breaks web tests.

This re-lands the change that adds focus nodes, hover, and shortcuts to switches, checkboxes, and radio buttons. (#43213)

No changes from original, except for finding the right RenderBox in dev/integration_tests/android_semantics_testing/test_driver/main_test.dart.

Revert "Add focus nodes, hover, and shortcuts to switches, checkboxes, and radio buttons. (#43213)" (#43367)

This reverts commit 90006720.

In order to enable keyboard navigation to more controls, I've added focus nodes to switches, checkboxes, and radio buttons. In addition, this change enables mouse hover over these controls.

- Added tests for focus, hover, and shortcut activation for Checkbox, Radio, and Switch.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

It was causing problems rolling Flutter into Fuchsia

Changes:

- Move the SemanticsConfiguration update from RenderToggleable to each subclass, so that Switch can use toggled.
- Add image, liveRegion, toggled properties to Semantics, SemanticsConfiguration, SemanticsNode
- Added semanticsLabel and excludeFromSemantics to Image (the latter so that we avoid creating a semantics node)
- Added onDismiss semantics action which maps to the modal escape on iOS and dismiss action on Android.
- Added dismiss and liveRegion to snackbar widget
- Updated custom painter semantics to handle image, liveRegion, toggle
- Updated relevant tests to use correct flag/action

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

This reverts commit 989f5741.

Revert longPress/Tap and Gallery changes

* Identify CHeckBox and RadioButton as such

* review feedback

**This PR contains a breaking API change:**
`SemanticsConfiguration.addAction()` has been removed and replaces by action-specific setters (`onTap`, `onLongPress`, etc.) to take care of the fact that some action handlers (those, who take arguments) have different signatures.