This reverts commit 5fd259be.

Migrate yet even more widget framework tests to null safety.

Remove fake image implementations, add createTestImage to flutter_test

* 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

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

* prefer_void_to_null in flutter_test

* fix CI

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

It was causing problems rolling Flutter into Fuchsia

Changes:

- Move the SemanticsConfiguration update from RenderToggleable to each subclass, so that Switch can use toggled.
- Add image, liveRegion, toggled properties to Semantics, SemanticsConfiguration, SemanticsNode
- Added semanticsLabel and excludeFromSemantics to Image (the latter so that we avoid creating a semantics node)
- Added onDismiss semantics action which maps to the modal escape on iOS and dismiss action on Android.
- Added dismiss and liveRegion to snackbar widget
- Updated custom painter semantics to handle image, liveRegion, toggle
- Updated relevant tests to use correct flag/action

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

This contains the following commit:

flutter/engine@cb3376c Support different encodings in Image.toByteData() (#16635)

This roll includes the following engine commits:

* flutter/engine@0c09bf03: In the service protocol, if no view is specified to flush tasks on, pick the first one. (#5028)
* flutter/engine@ecaefd7a: Roll src/third_party/skia/ 276886160..1cd6098d5 (50 commits) (#5026)
* flutter/engine@e6545573: Enable 'Speak Screen' and 'Switch Control' for iOS (#5016)
* flutter/engine@3393c179: Fix Android platform channels (#5025)
* flutter/engine@1bc0e1bb: On windows, refer to Dart snapshot directly executable. (#5024)
* flutter/engine@cf6ca32d: Revert "Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79" (#5023)
* flutter/engine@4b45a53e: Only make ERROR and FATAL log levels visible by default. (#5022)
* flutter/engine@98f6c2d5: Fix shell launcher test (dart2 compliant and stop polling) (#5009)
* flutter/engine@75851f08: Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79 (#5020)
* flutter/engine@9495a52d: On iOS, try to use ES3, then fall back to ES2. (#5006)
* flutter/engine@d6d4eec2: Fix broken Linux build (#5019)
* flutter/engine@d15dc76e: Fix broken Chromebot build (#5018)
* flutter/engine@c17a6290: Breadcrumbs to the wiki (#5017)
* flutter/engine@4eaf2c2f: Return raw (unencoded) bytes in Image.toByteData() (#5008)
* flutter/engine@d812a617: Roll src/third_party/skia/ e669bdfad..276886160 (9 commits) (#5014)
* flutter/engine@62aeab72: Call SkSurface::flush instead of getting a backend handle in vulkan_swapchain. (#5012)
* flutter/engine@f4ebb180: Roll src/third_party/skia/ 3462eb034..e669bdfad (54 commits) (#5007)
* flutter/engine@0b7d6be9: Re-land "do not pause rendering when android view loses focus" (#5004)
* flutter/engine@91dee598: If the rasterizer has a valid surface context, use that to create a snapshotting render target. (#4979)
* flutter/engine@570231b7: Specify the packages file path when running engine dart tests. (#5005)
* flutter/engine@0b9cef5a: Minor update to README (#5003)
* flutter/engine@c386418f: Promote line height in text style created from paragraph style (#4995)
* flutter/engine@4e0fbb6f: If the test specifies a .dill file, dont make the engine interpret is as source. (#5002)
* flutter/engine@58e84c8b: Re-land "Support multiple shells in a single process. (#4932)" (#4998)
* flutter/engine@37e5df05: Remove only use of SkPaint::kGenA8FromLCD (#4994)
* flutter/engine@b7358b33: libtxt: cache font families that are remapped to the default font family (#4990)
* flutter/engine@a530035b: libtxt: fix leaks in Skia object reference counting (#4988)
* flutter/engine@0c74fc93: [fuchsia] Fix use-after-free (#4987)
* flutter/engine@b6d2dde9: [fuchsia] Fix build (#4986)
* flutter/engine@1dd12649: [async] Adapt to libasync API changes. (#4980)