Fixes #7519

Fixes https://github.com/flutter/flutter/pull/8643

Fixes https://github.com/flutter/flutter/issues/8804 by adding a test
to verify that Material elevation changes animate.

Also tweak some dartdocs, add some trailing commas, improve some
toString output, make the inkwell test agnostic to the PhysicalModel
logic, and move the material buttons test to the material test
directory.

The Wrap widget is a layout that places children in a run in order along its
main axis until it runs out of space. At that point, starts placing children in
a new run that is adjacent in the cross axis.

Fixes #8831

Also adds a test to make sure we don't break it again.

This yak shave went as follows:

Fix https://github.com/flutter/flutter/issues/8795 by adding stocks to
the examples README.

Notice the layers entry in that README isn't quite right either.
Update that.

Check the layers/README file is worth pointing at.

Update the layers/README.

Let's run some of the layer tests to see if they still work.

Oops, need to update them to gradle.

Ok let's try running them again.

Oops, sector is broken.

Add a test for sector.

Fix sector. Find you need to add an assert to a const constructor.

Notice we need to turn const asserts on for the analyzer.

Notice the analysis_options files are out of sync with each other and
with the full list of lints.

Turn on the lints that should be on.

Fix the bugs that finds.

* Roll Dart to 1.23.0-dev.11.3.

This is expected to fix the Windows crashes reported in https://github.com/flutter/flutter/issues/8912.

* fix tests

* Roll to 1.23.0-dev.11.5

* Fix tests

Mostly related to semantics and scrolling.

Add some commentary around DefaultTabController.initialIndex.
Fix typo (nuull) in TabBar.
Make some asserts more detailed.

* Add tolerance argument to FrictionSimulation.
* Change FrictionSimulation.through to setting tolerance
  via the constructor rather than afterwards.
* Allow SimulationGroup constructor to take tolerance argument.
* Add a toString for SpringDescription.
* Add a toString for SpringSimulation.
* Push this change to BouncingScrollSimulation.

This issue is being tracked at: https://github.com/dart-lang/sdk/issues/29230

Fixes https://github.com/flutter/flutter/issues/9186

This package now depends on collection and quiver. The package level
dependencies in the BUILD.gn file should match the list of dependencies
in the pubspec.yaml file for the Fuchsia build to function.

* Just realized the creation order is the other way around

* Works

* Revert previous partial solution

* Change pumpAndSettle to pump for gestures

Uninstalling the app removes the data and cache directories, so this
allows application data to persist across multiple flutter run
invocations.

This also handles the edge case where the app fails to install due to an
error in installation (e.g. debug keystore changes, switching from a
release keystore to a debug keystore, etc.).

* Make IntelliJ metadata files consistent with the current flutter create template

* Add missing IJ files from current flutter create template

* Remove run config from layers as it requires running with -t

* Remove workspace.xml files per review feedback

Gradle projects are evaluated in lexicographical order, and the plugin
projects are at the same level as the :app project, so if a plugin has
a name that comes before 'app' (like, for example, any name that starts
with a capital letter), the plugin project will be evaluated before
:app.

Since :app applies the Flutter Gradle plugin, which tries to
modify the dependencies of the plugin projects, we have a problem if the
plugin projects have already been evaluated. Adding
evaluationDependsOn(':app') to the plugin projects fixes this.

Updated example projects to the latest (plugin-enabled) Gradle build
files.

Also removed two unused imports in `pluginClass.java.tmpl`.

* Add new metric to size_tests instead

* Small lints

The underlying issue was fixed by the new focus system.

Fixes #1523

This patch adds docs for many of the sliver widgets.