* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test

* Visibility widget

This attempts to address the confusion around how to hide a widget subtree.

* Apply review comments

* More clarifications

This fixes https://github.com/flutter/flutter/issues/18057

See details in our proposal for this breaking API change and #18057. This PR setup all code paths to allow the change but doesn't change the clip behavior by itself. We'll change `defaultClipBehavior` from `Clip.antiAlias` to `Clip.none` in the following PR to change the clip behavior and update tests.

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.

* Use RenderAnimatedOpacity within AnimatedOpacity widget (#15466)

* Fixed minor bug in RenderAnimatedOpacity

* Updated protected API for ImplicitlyAnimatedWidget

The new matcher package deprecates isInstanceOf which seems eggregious.

We have many hidden children because of iOS accessibility (see also #18410).

For example, in the tile screen of complex_layout app, there could be up to 20 children being painted without this PR. With this PR, only 12 get painted.

This should improve the performance of FL-53 by 40%.

fuchsia_tester.dart still assumes Dart 1. Previously, it ran tests directly
from source, flutter_platform.dart automatically runs a kernel compile when
operating in Dart 2 mode, but this assumes a functional Dart SDK is available
in the artifacts directly, and fuchsia_tester.dart mocks out the artifacts
directory with an empty temp dir.

Remaining work is:
1. Get the frontend server building as a dependency on Fuchsia.
2. Patch fuchsia_tester.dart to use a valid Dart SDK and frontend server.

This also reverts migration to Dart 2 typedef syntax.

This reverts commit 6c56bb24. (#18362)
This reverts commit 3daebd05. (#18316)

Now that Dart 1 is turned off, reapplying my change to turn on the prefer_generic_function_type_aliases analysis option, and fix all the typedefs to Dart 2 preferred syntax.

Also eliminated the unused analysis_options_repo.yaml file and turned on public_member_api_docs in analysys_options.yaml.

No logic changes, just changing the typedef syntax for all typedefs, and updating analysis options.

Revert "Update typedef syntax to use Function notation and turn on lint for old notation. (#18035)" (#18041)

This reverts commit 32586020.

Fixes #18028

Just changes typedef declarations, no logic changes.

It allows callers to account for things like shadows that paint
outside the bounds of the widget.

https://github.com/flutter/flutter/issues/16859

This adds a toImage function to RenderRepaintBoundary that returns an uncompressed raw image of the RenderRepaintBoundary and its children. A device pixel ratio different from the physical ratio may be specified for the captured image. A value of 1.0 will give an image in logical pixels.

This addresses #16593 by removing the unneeded assert in the setter for constrainedAxis. Null was meant to be allowed there.

This replaces #16599 and fixes #16593, reported by @maksimr

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)

* Roll engine to d6d4eec24c38bb06a9b1aef4e70c321d447ba762

Contains the following engine commits:

flutter/engine@1bc0e1b On windows, refer to Dart snapshot directly executable.
flutter/engine@cf6ca32 Revert "Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79"
flutter/engine@4b45a53 Only make ERROR and FATAL log levels visible by default.
flutter/engine@98f6c2d Fix shell launcher test (dart2 compliant and stop polling)
flutter/engine@75851f0 Roll Dart to fe606f890b0a311da802c78b0af414a3c2087a79
flutter/engine@9495a52 On iOS, try to use ES3, then fall back to ES2.
flutter/engine@d6d4eec Fix broken Linux build
flutter/engine@d15dc76 Fix broken Chromebot build
flutter/engine@c17a629 Breadcrumbs to the wiki
flutter/engine@4eaf2c2 Return raw (unencoded) bytes in Image.toByteData()
flutter/engine@d812a61 Roll src/third_party/skia/ e669bdfad..276886160 (9 commits)
flutter/engine@62aeab7 Call SkSurface::flush instead of getting a backend handle in vulkan_swapchain.
flutter/engine@f4ebb18 Roll src/third_party/skia/ 3462eb034..e669bdfad (54 commits)
flutter/engine@0b7d6be Re-land "do not pause rendering when android view loses focus"
flutter/engine@91dee59 If the rasterizer has a valid surface context, use that to create a snapshotting render target.
flutter/engine@570231b Specify the packages file path when running engine dart tests.
flutter/engine@0b9cef5 Minor update to README
flutter/engine@c386418 Promote line height in text style created from paragraph style
flutter/engine@4e0fbb6 If the test specifies a .dill file, dont make the engine interpret is as source.
flutter/engine@58e84c8 Re-land "Support multiple shells in a single process.
flutter/engine@37e5df0 Remove only use of SkPaint::kGenA8FromLCD
flutter/engine@b7358b3 libtxt: cache font families that are remapped to the default font family
flutter/engine@a530035 libtxt: fix leaks in Skia object reference counting
flutter/engine@0c74fc9 [fuchsia] Fix use-after-free
flutter/engine@b6d2dde [fuchsia] Fix build
flutter/engine@1dd1264 [async] Adapt to libasync API changes.

* Run test platform finalizers in reverse order to ensure that shell is shutdown before trying to delete any temporary files or directories. This fixes "Access Denied" error on Windows (see #16657).

This fixes a rendering problem in the AnimatedChildSwitcher where it would add a new "previous" child each time it rebuilt, and if you did it fast enough, all of them would disappear from the page.

It also expands the API for AnimatedChildSwitcher to allow you to specify your own transition and/or layout builder for the transition.

Fixes #16226

* Upgrade packages to pull in newest petitparser with Dart 2 fixes.

* Don't allow Dart 2 failures.

* Address new lints discovered by updated analyzer.

* Roll engine to b6df7a637498ca9beda1fa9cd7210e3202ea599f.

Changes since last roll:
```
b6df7a637 Roll dart to 290c576264faa096a0b3206c71b2435309d9f904. (#4771)
a6764dbd5 Add sources for Fuchsia target. (#4763)
2d5900615 [fuchsia] Remove unused header file. (#4769)
9717063b7 Revert "Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)" (#4768)
9a9814312 Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)
e74e8b35c [async] Update includes of async headers to new path (#4760)
e2c4b2760 Use Dart 2 camel case constants in the engine Dart libraries (#4766)
9c1e48434 Updates for Fuchsia roll. (#4765)
14c940e27 Switch from fxl::Mutex to std::mutex (#4764)
debf82c0b Roll Garnet (#4759)
5bffdefbb Use weak pointers to the accesibility bridge from objects vended to the UIKit accessibility framework. (#4761)
```