This reverts commit 4518a72f.

* migrate part of painting to nullsafety

* address review comments

* address review comment

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

* Remove listeners for live images when we clear them

* review, more test

* explanation

* Reland "Live image cache" (#51441)

This reverts commit 419a2853.

* Make evict safer

* Revert "Live image cache (#51249)"

This reverts commit e2dcdb60.

* fix tests for other commit

* Revert "Revert "Live image cache (#50318)" (#51131)"

This reverts commit 2f09d601.

* Fix eviction of a pending image

This reverts commit 1602be6a.

Track images available on screen

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

This reverts commit 86dd664f.

Introduced LargeImageHandler to ImageCache class.

* 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

It was easy to miss the reference to the top-level `imageCache`
property before.  This calls out the property a little more
explicitly.

The current API was broken in that you registered multiple
callbacks at once, but when you removed listeners, only the
primary listener was used to determine what was removed.
This led to unintuitive cases where the caller could get
unexpected behavior.

This updates the API to add and remove listeners using
a newly introduced [ImageStreamListener] object, a value
object that has references to the individual callbacks
that may fire.

flutter/flutter#24722
flutter/flutter#32374
flutter/flutter#32935

* Ensure all errors thrown by image providers can be caught by developers.

Add an `onError` parameter to the ImageCache.putIfAbsent method.
In the event that an error is thrown when resolving an image, catch if
this parameter is provided. Use the onError parameter to ensure that all
errors thrown are forwarded to the ImageStream error channel instead of
directly into the void.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

This should fix #18952 and #813

This allows the scheduler library to depend on the services library
and the painting library to depend on the scheduler library without
the services library having to depend on the scheduler library.

While I was at it I also cleaned up some of the binding logic: the
licenses logic can now be overridden (and the test library does so),
and the image cache can now be overridden as well.

when describing non-nullable method arguments.

...so that you can use hot reload mode to update assets.