* migrate material to nullsafety

* address review comments

* address review comments

* fix build

* Add punctuation for unterminated sentences in doc comments

* Addressing review nit

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

This reverts commit 2132a0c7.

This reverts commit 69080e07.

[a11y] Make sure RenderFractionalTranslation updates its semantics after the translation field is set (#48985)

* 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

* fix indentof statements in BlockFunctionBody

* fix indentof statements in BlockFunctionBody in tests

This converts existing ## Sample code samples to {@tool sample}...{@end-tool} form.

Also:
1. Fixed a minor bug in analyze-sample-code.dart
2. Made the snippet tool only insert descriptions if the description is non-empty.
3. Moved the Card diagram to before the code sample.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

* lint unnecessary_new on samples

* fix tests

- remove an //ignore that is no longer needed
- fix some intrinsic methods that used the API incorrectly (shouldn't affect correctness but should make things a tiny bit more efficient)
- add some asserts to help track down bugs quicker
- update a TODO to point to the currently relevant bug
- fix some indenting
- improve the naming of some privates to improve readability

Segment width now determined by width of widest child + children widgets now centered within segments

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.