~~Using the same priority order as a Border without borderRadius, it is possible to draw them on top of each other. This is better than the current behavior (crash!) and would work well for a "one color on top, another on bottom" scenario.~~

~~With this, if approved, we move the current number of possible exceptions from 4 to 1 (`BoxShape.circle` + `borderRadius`).~~

~~It is kind of odd how `borderRadius.zero` to `borderRadius != BorderRadius.zero` change, but I think it is better than crashing. Alternatively, we just remove the "original function" and see if any goldens are affected.~~

<img width="448" alt="image" src="https://user-images.githubusercontent.com/351125/236550350-7499d758-5b44-40e6-9105-32671eb21998.png">

Another one for @gspencergoog. If this works, we could make the paint method public and re-use in the InputBorder PR (if that's also approved). Single line fix.

Fixes https://github.com/flutter/flutter/issues/59413

This relocates `mock_canvas.dart` and `recording_canvas.dart` from `flutter/test/rendering` to `flutter_test`. 

The testing functionality afforded by mock_canvas should be available to everyone, not just the framework. :)

mock_canvas.dart needed a bit of cleanup - things like formatting and super parameters.

Updated unit tests for `Divider`/ `VerticalDivider`  and theme to have M2 and M3 versions.

More info in https://github.com/flutter/flutter/pull/128725

Updates most of the unit tests in the packages/flutter/test/material folder so that they'll pass if ThemeData.useMaterial3 defaults to true.

All of the tests have wired useMaterial3 to false and will need to be updated with a M3 version.

related to #127064

* Make Flex,Row,Column const for real

* dart fix --apply

* fix snippets

* fix integration test

* add comment

* 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

* Fixed indent to properly add to the top and not to the start

* Updated Divider documentation

* Vertical divider bug fix and additional cleaning.

* Add vertical divider option.

* added vertical divider

* restored hello world

* final changes

* a few changes

* comment fixes

* added VerticalDivider

* few changes

* comment changes:

* ultra nits

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

Fix a bunch of obvious RTL bugs from code inspection.

* Make dividers one device pixel thick as defined in Material design spec

* Updated divider test to check stroke width

* Clarified dividers with 0 height in the docs

* Updated Divider.height docs according to PR feedback

* more widget const constructors

* prefer const constructors

* address review comments

Previously these widget had zero test coverage. Also, improve the
coverage tooling Mac.