* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

This reverts commit 11efa00f.

* reland "Refactors global key duplication detection (#46183)"

This reverts commit d2b66dbf.

* fix test

This reverts commit 340b193f.

This reverts commit 04ea3183.

This reverts commit e768c92f.

* Update packages.

* Add many more global analyses.

* Catch trailing spaces and trailing newlines in all text files.
  Before we were only checking newly added files, but that means we
  missed some.

* Port the trailing spaces logic to work on Windows too.

* Correct all the files with trailing spaces and newlines.

* Refactor some of the dev/bots logic into a utils.dart library.
  Notably, the "exit" and "print" shims for testing are now usable
  from test.dart, analyze.dart, and run_command.dart.

* Add an "exitWithError" function that prints the red lines and
  then exits. This is the preferred way to exit from test.dart,
  analyze.dart, and run_command.dart.

* More consistency in the output of analyze.dart.

* Refactor analyze.dart to use the _allFiles file enumerating logic
  more widely.

* Add some double-checking logic to the _allFiles logic to catch
  cases where changes to that logic end up catching fewer files
  than expected (helps prevent future false positives).

* Add a check to prevent new binary files from being added to
  the repository. Grandfather in the binaries that we've already
  added.

* Update all the dependencies (needed because we now import crypto in
  dev/bots/analyze.dart).

* implicit-casts:false in flutter/lib/src/widgets

* address review comments

* address review comment

* 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

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

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

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

This reverts commit 9aea03f4.

* Minor improvements to framework documentation.

* maybePop documentation fix

* Mark some flutter_test arguments required.

Without these set, we get a crash.

* Minor correction to ListView docs

Fixes the hasScrollBody flag not accounting for child size. Adds the ability to specify over-scroll behavior.

* WIP

* Fixing nested scroll view tests

* Fixing nested scroll view tests

* Fixing nested scroll view tests

* WIP

* Added flag for SliverFillRemaining

* Clean up

* Review

* Reverted nested scroll view tests

* Updating tests

* Updated for overscroll behavior

Add a more meaningful message to the assertion on children property of MultiChildRenderObjectWidget and SliverChildListDelegate. (#32487)

Make FlutterError objects more structured so they can be displayed better in debugging tools such as Dart DevTools.

This reverts commit 77ab0b83.

Credit to @ymback

* fix some formatting issues

* address review comments

* fix indent

Fix the spelling errors in the dartdocs for the framework.

There are no functionality changes here, just documentation fixes.