This reverts commit d056500b.

This reverts commit 31de052e.

This reverts commit e2490f29.

The FocusManager constructor was registering global event handlers
on the shared RawKeyboard instance and the global pointer router.
This posed a few problems: (1) there was no way to unregister these
handlers, and (2) instantiating a second FocusManager would overwrite
the existing focus manager's RawKeyboard handler. This was manifesting
in unexpected ways, such as the fact that constructing a second
BuildOwner (for a parallel tree, for instance) was obliterating the
event handler for the main BuildOwner's focus manager, thus messing
with focus.

This change separates those global event registrations into a
dedicated method, registerGlobalHandlers(), and overrides dispose()
to properly unregister those handlers.

This call is unnecessary and wasteful for callers that are building
parallel widget trees, since for those use cases, the caller is
generally going to build the tree synchronously immediately.

This can be useful for offscreen widget trees, where the caller
wants to completely tear down the tree (properly clean up) when
they're done with the tree, to ensure they're not leaving behind
any event listeners that could be registered by child elements
(which could lead to memory leaks and unexpected behavior).

Migrate yet even more widget framework tests to null safety.

* add language version 2.8 in packages/flutter

* enable non-nullable analyzer flag

* add key to constructors of public widgets

* fix a test

* fix a test

* 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

* enable lint unnecessary_new

* fix tests

* fix tests

* fix 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.

Separate focus management by build owner

Currently the focus manager is held by the singleton WidgetBinding.
This change places a focus manager in each build owner object,
which allows clients to run offscreen pipelines without disturbing
focus management for the main UI.

* make @immutable const

* fix build

Rename State.config to State.widget
Rename State.didUpdateConfig to State.didUpdateWidget
Renamed all State subclasses' local variables named config to something else

Previously, if a StatefulWidget was marked dirty, then removed from the
build, then reinserted using the exact same widget under a widget under
a LayoutBuilder, it wouldn't rebuild.

This fixes that.

It also introduces an assert that's supposed to catch SizeObserver-like
behaviour. Rather than make this patch even bigger, I papered over two
pre-existing bugs which this assert uncovered (and fixed the other
problems it found):

   https://github.com/flutter/flutter/issues/5751
   https://github.com/flutter/flutter/issues/5749

We should fix those before 1.0 though.

Also, make SemanticsOwner into a real class and use it instead of a static in
several places.

This makes it possible to substitute 'flutter run' for 'flutter test'
and actually watch a test run on a device.

For any test that depends on flutter_test:

1. Remove any import of 'package:test/test.dart'.

2. Replace `testWidgets('...', (WidgetTester tester) {`
      with `testWidgets('...', (WidgetTester tester) async {`

3. Add an "await" in front of calls to any of the following:
    * tap()
    * tapAt()
    * fling()
    * flingFrom()
    * scroll()
    * scrollAt()
    * pump()
    * pumpWidget()

4. Replace any calls to `tester.flushMicrotasks()` with calls to
   `await tester.idle()`.

There's a guarding API that you can use, if you have particularly
complicated tests, to get better error messages. Search for
TestAsyncUtils.