This logic is described in the test as looking for a scroll ending
very close to a new page, but in fact its behavior is more like
"very close to a page to the right": if we're not very, very close
to any page, it will pick the page to the left, not an old page.

There's no reason this should be left-right asymmetrical.
Instead, pick the nearest page.

In practice, the case where this makes a difference never arises when
the scroll runs undisturbed to completion; but when the user taps on
the page to hold or drag, the scroll will be interrupted before it
gets within tolerance of a particular page, and this case does arise.

This fixes a glitch that is hard to trigger without time dilation,
but is quite conspicuous with it:

 * Open a tab view with at least 4 tabs, e.g. the Buttons screen
   of the gallery (with "Animate Slowly" on.)
 * Starting at tab 0, tap tab 2.
 * When the animation is nearly complete, tap the page a couple
   of times, as if to drag it around to scroll.  Then let the
   page view settle ballistically toward page 2.
 * Before it finishes, tap tab 3.
 * Suddenly page 1 fills the view, replacing page 2, before we
   scroll from there to page 3.

With this fix, the animation in the last step moves smoothly from
where we are when it starts onward to page 3.

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.

Fixes https://github.com/flutter/flutter/issues/16169

For example, mention the icon used for the drawer menu in the docs (this helps people writing unit tests); add DefaultAssetBundle sample code.

* localize a11y tab labels in the TabBar

* break import cycle

* test boilerplate

* fix German translation

* more test boilerplate fixes

I got tired of drive-by spelling fixes, so I figured I'd just take care of them all at once.

This only corrects errors in the dartdocs, not regular comments, and I skipped any sample code in the dartdocs. It doesn't touch any identifiers in the dartdocs either. No code changes, just comments.

* enable lint prefer_const_constructors_in_immutables

* remove LabeledGlobalKey._

* Oct 12 10:12am

* implicit_semantics_test.dart passes

* refactoring

* works in nice

* minor rename

* more doc comments

* to be explicit check better

* fix test

* ++

* ++

* semantics_9_test (BlockSemantics) and implicit_semantics_test are passing

* doc updates

* tiny refactor

* fix static errors in tests

* fix gesture detector

* ++

* ++

* geometry

* ++

* remove noGeometry

* revert test

* +

* all tests but scrolling/clipping pass

* clipping works

* scrolling halfway

* sliver tests pass

* ALL TESTS PASS

* SemanticsNode changed

* docs and tiny fixes

* card test

* more doc comments

* remove missed print

* more tests

* make test pass on Linux

* remove changes to intellij proj file

* review comments

* Make Tab take a widget as child

This way you can override the semantics information of a Tab (see test).

Fixes https://github.com/flutter/flutter/issues/12432

* more tests

* review comments

* review comment

* doc nits

* style fix

* Fix inherited widget notifications in Localizations

* address comments

* Introduce a Directionality inherited widget which sets the ambient LTR vs RTL mode (defaulting to null, which means you cannot use directionality-influenced values).

* Make it possible to configure Padding (including Container.padding and Container.margin) using a directionality-agnostic EdgeInsets variant.

* Provide textDirection and verticalDirection controls on Row and Column to make them RTL-aware.

* Introduce a variant of FractionalOffset based on the EdgeInsets variant. Not yet actually used.

* Fix all the tests that depended on Row defaulting to LTR.

when describing non-nullable method arguments.

* Allow tapping on TabBar indicator to switch tabs

* fix semantics

* review comments

Add Diagnosticable base class and documentation

Refactor RenderObject.toStringDeep and Widget.toStringDeep code to use DiagnosticsNode.

* [accessibility] Announce index if tab in tab bar

* added TODO

* Add SemanticsNode.isSelected flag

* Adds example usage to TabBar

See also https://github.com/flutter/engine/pull/3764

* Review comments

* whitespace fixes

* Fix doc ref and update engine roll

Moved everything icons related except the material icon button and the materialicon font list to widget

This patch finishes documenting all the symbols except for those related to
scrolling.