This reverts commit c59151b1.

This PR rewrites MouseTracker's lifecycle, so that mouse callbacks are all triggered in post frame, instead of the current one where some are triggered during the build phase. This PR also changes the onExit callback to MouseRegion, RenderMouseRegion, and MouseTrackerAnnotation, so that it is no longer triggered on dispose.

Revert "Track and use fallback TextAffinity for null affinity platform TextSelections. (#44622)" (#45698)

This reverts commit 6b66d794.

* 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 appears to have been inadvertently added in #37497 (333c9618).

The code in question already exists in `_PlatformViewGestureMixin`, which
`PlatformViewRenderBox` (where it was added) mixes in.

Removes an unnecessary leading underscore from a parameter name. The
parameter type is library private, but parameters cannot be 'private'.

Fixes https://github.com/flutter/flutter/issues/45587

This PR adds TargetPlatform.macOS to the TargetPlatform enum. This allows us to begin implementation of some adaptive UI based on which target platform is desired.

I haven't updated the tests here, that will come in a follow-up PR.

No code changes, just comments: I spell-checked all the comments in the repo.

This reverts commit d285b884.

This adds support for the command key for text selection/editing on macOS. I had ported the text editing code (in #42879), but forgot to add support for the command key itself. This also adds a test that tests the text editing on multiple platforms instead of just testing Android.

There appears to still be a bug (filed #44135) where we're losing key events sometimes on macOS, leaving some keys "stuck" on, but this PR at least allows the right key combinations to be used.

Revert "Implement PageView using SliverLayoutBuilder, Deprecate RenderSliverFillViewport (#37024)" (#44778)

* Revert "Implement PageView using SliverLayoutBuilder, Deprecate RenderSliverFillViewport (#37024)"

This reverts commit 9aea03f4.

* Add opaque to barriers
* Detect opaque and test

SliverAppBar - Configurable overscroll stretch with callback feature & FlexibleSpaceBar support (#42250)

* Add structured errors in Animations, TabView, ChangeNotifier

* Add structured error on MaterialPageRoute, BoxBorder, DecorationImagePainter, TextSpan

* Add structured errors in Debug

* Fix test errors

* Add structured errors in Scaffold and Stepper

* Add structured errors in part of Rendering Layer

* Fix failing test due to FloatingPoint precision

* Fix failing tests due to precision error and not using final

* Fix failing test due to floating precision error with RegEx instead

* Add structured error in CustomLayout and increase test coverage

* Add structured error & its test in ListBody

* Add structured error in ProxyBox and increase test coverage

* Add structured error message in Viewport

* Fix styles and add more assertions on ErrorHint and DiagnosticProperty

* Add structured error in scheduler/binding and scheduler/ticker
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured error in AssetBundle and TextInput
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured errors in several widgets #1
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Remove unused import
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add assertions on hint messages
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Fix catch spacing
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured error in several widgets part 2 and increase code coverage
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured error in flutter_test/widget_tester

* Fix floating precision accuracy by using RegExp
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Remove todo to add tests in Scaffold showBottomSheet
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Fix reviews by indenting lines and fixing the assertion orders
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Fix failing tests due to renaming class
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Try skipping the NetworkBundleTest
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Remove leading space in material/debug error hint
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Replace hard break of Layer.find/All with findAllAnnotations
* Deprecate findAll

This re-implements keyboard text selection so that it will work on platforms other than Android (e.g. macOS, Linux, etc.).

Also, fixed a number of bugs in editing selection via a hardware keyboard (unable to select backwards, incorrect conversion to ASCII when cutting to clipboard, lack of support for CTRL-SHIFT-ARROW word selection, etc.).

Did not address the keyboard locale issues that remain, or add platform specific switches for the bindings. All that will need some more design work before implementing them.

Related Issues
Fixes #31951

The _computeChildren[Width/Height]With[Min/Max]Intrinsics methods in
RenderParagraph overwrite the text painter's placeholder dimensions
in order to compute potential widths and heights for the paragraph.

The placeholder dimensions should be restored to the values computed by
_layoutChildren before painting the text.

* Adds a new parameter bool opaque to MouseRegion
* The same to RenderMouseRegion and AnnotatedRegionLayer
* Add findAnnotations to Layer 

This adds a Semantics node to the Focus and FocusScope widgets, setting the focused and focusable attributes so that the accessibility subsystem can be told when a control has the input focus.

Includes an engine roll to flutter/engine@77252d2, and the following 8 engine changes:

flutter/engine@77252d2 Greg Spencer Add missing focusable testing info (flutter/engine#13013)
flutter/engine@0e42a29 skia-flutter-.. Roll src/third_party/skia 54548626a977..e27a503a0a21 (1 commits) (flutter/engine#13024)
flutter/engine@6b56ed7 gaaclarke Refactor: FlutterDartProject (flutter/engine#13006)
flutter/engine@393480c skia-flutter-.. Roll src/third_party/skia 77dde599c98a..54548626a977 (1 commits) (flutter/engine#13023)
flutter/engine@080b89d skia-flutter-.. Roll src/third_party/skia 2b1a25a4d324..77dde599c98a (1 commits) (flutter/engine#13021)
flutter/engine@90b0f30 Ben Konyi Roll src/third_party/dart f4a72bfc64..bb04f145b2 (18 commits) (flutter/engine#13020)
flutter/engine@049fb89 skia-flutter-.. Roll fuchsia/sdk/core/linux-amd64 from q_uYX... to cknsi... (flutter/engine#13019)
flutter/engine@6925b2a skia-flutter-.. Roll fuchsia/sdk/core/mac-amd64 from wuAtw... to u0JpE... (flutter/engine#13018)

Related Issues
Addresses #40101

Landing on red in order to fix the build: it's red because of the needed engine roll.