* Added new ButtonBarTheme to replace the deprecated ButtonTheme.bar method.

* Responding to PR feedback.

* [Material] Create material Banner component (#36880)

This PR creates a new material widget for the Banner component. This includes a theme as well. This widget can be dropped into any application, ideally at the top of a listview or scrollview.

(cherry picked from commit 35b6d668)

Removed the use of ButtonTheme.bar in the Banner implementation.

* Updated documentation from PR review comments.

* 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

* Minor UI tweaks to Cards demo based on internal feedback

* Analyzer

* Tweak ink ripple opacity

* Address PR feedback

[Material] Update the card demo in the Gallery to demonstrate different uses of the Card widget (#27699)

Additionally, this adds a tappable Card example to the Card documentation.

ButtonThemeData no longer requires a colorScheme. If colorScheme is null, ButtonTheme.of() will initialize it from the current Theme.

* Update uses of ButtonTheme.bar

* updated gallery themes

* Remove unnecessary const

Fixes #22789

* 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.

* spelling: accommodate

* spelling: allotted

* spelling: anonymous

* spelling: artificial

* spelling: associated

* spelling: asset

* spelling: button

* spelling: canvas

* spelling: compatibility

* spelling: coverage

* spelling: condition

* spelling: decoration

* spelling: deferring

* spelling: diameter

* spelling: direction

* spelling: displacement

* spelling: dropdown

* spelling: needing

* spelling: environment

* spelling: exited

* spelling: expansion

* spelling: explore

* spelling: families

* spelling: horizontal

* spelling: increment

* spelling: indices

* spelling: internationalization

* spelling: labrador

* spelling: localizations

* spelling: midflight

* spelling: milliseconds

* spelling: minimum

* spelling: multiple

* spelling: multiplication

* spelling: navigator

* spelling: overridden

* spelling: package

* spelling: performance

* spelling: platform

* spelling: porsche

* spelling: position

* spelling: preceded

* spelling: precede

* spelling: precedence

* spelling: print

* spelling: property

* spelling: readily

* spelling: reproducibility

* spelling: rounded

* spelling: scroll

* spelling: separate

* spelling: separator

* spelling: services

* spelling: specific

* spelling: specify

* spelling: synchronously

* spelling: through

* spelling: timeout

* spelling: triangle

* spelling: trivial

* spelling: unusual

* spelling: then

* spelling: vertically

* spelling: visible

* spelling: visited

* spelling: voice

Applies media padding (e.g. iPhone X safe area insets) to the Material Design demos in the Gallery.

Covers the following demos:
* Buttons (via the TabbedComponentDemoScaffold change)
* Cards
* Expansion panels
* Grid list
* Icons
* Images (via the TabbedComponentDemoScaffold change)
* Page Selector
* Progress Indicator
* Scrollable tabs
* Selection controls (via the TabbedComponentDemoScaffold change)
* Snack bar
* Tabs
* Text fields
* Tooltips

Fixes #13594

Alignment will eventually replace FractionalOffset.

Minor fixes throughout, e.g. removing trailing commas from the end of sample code expressions, changing headings to "sample code" more consistently, removing stale todos, fix typos in a private method name, minor grammar fixes, added some clarifications to CircularProgressIndicator, LinearProgressIndicator, CrossAxisAlignment, added some cross-references to various members, made it slightly clearer that layout algorithms are implementation details.

Clarified "elevation" throughout.

Added docs to InkResponse and InkWell.

Added sample code for: SliverAppBar, Card, ListTile, EdgeInsets, Row, Column, CustomScrollView, ListView, SliverFixedExtentList, and SliverGrid.

Fixes #10317.
Fixes #10316.
Fixes #10267. (sort of, see comment therein)
Fixes #9331. (sort of, see comment therein)
Fixes #9407. (sort of, see comment therein)

Aggressively apply the const lint.

* add @required when there's an assert not null

* address review comments

This machinery is useful for arbitrary boxes (e.g., with FittedBox).

Fixes #6463

* Add cupertino to gallery and add CupertinoButto

* Use single quotes

* Add disabled state

* Some review notes

* Make button animation more responsive and tweak timing

* Renamed things Cupertino

* Button with background, move cupertino demos, move material demos

* Move 2 level list too

* Refactor various demo route names

* Some review notes

* More reviews and add test

* Linter as

* Move private constant up

This prepares us for a CustomScrollView that takes slivers.

Now that ScrollView supports itemExtent, we can use it in a few more places.

This patch replaces uses of Flexible with Expanded where we're using
FlexFit.tight. We still need to think of a better name for the
FlexFit.loose variant.

Also, improve the docs for Row, Column, Flex, and RenderFlex to be more
problem-oriented and to give a complete account of the layout algorithn.

Fixes #6960
Fixes #5169

Renames stretch constructor to fill for better consistency with
the rest of the framework.