* Allow FloatingActionButton to not have a heroTag.
* Allow FloatingActionButton to not have a child.
* Allow Tooltip to not have a child.
* Improve the debug output of the default FloatingActionButton hero tag.
* Improve the error message in the Hero clashing-tag case.
* Improve the debug output of the Hero widget.
* Improve the debug output of gesture-related widgets.
* Minor improvements to documentation.
* Fix some typos in comments.
* Fix some style nits.

Diagnostics object is.

Some widgets are using closures even if the only values that are
captured are this, context or widget, that can be accessed even from
methods of the State object.

Add Diagnosticable base class and documentation

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

* AutomaticKeepAlive

A Widget that listens for notifications from widgets that don't want to die.

* Automatically wrap SliverList and SliverGrid children in AutomaticKeepAlive widgets

* Fixes for review comments

* Provide haptic/acoustic feedback for tap & long-press on Android

* review comments

* fixed example code

* review comments

* comment fix

You can't have a newline between the `]` and the `(` in an image in markdown it turns out.

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)

* 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

* adds border radius to ink widgets. sets default ink border radius for material buttons with no background colors

* tidying up code

* add ink test stub

* remove unused import

* adds highlight + splash color properties to material button

* add states to raised button + flat button

* fixes an issue where the custom highlight would not be properly set

* Add preliminary tests for theme highlight + splash and via theme

* documentation changes. tweaks per code review feedback

* comment out unused variable

* remove unused import

* documentation updates. removed commented code

Previously, these classes where in material.dart, which meant they could
access private interfaces in that library. This patch moves them out
into their own files so that they need to play by the rules of the
public API.

Fixes #5969

Fixes https://github.com/flutter/flutter/issues/5763

We have these details objects for the same reason we now have drag details
objects: future extensibility.

Fixes https://github.com/flutter/flutter/issues/3493

 - rebuild stateless widgets that have dependencies when their ancestors change but they don't

Fixes https://github.com/flutter/flutter/issues/3120

 - rebuild widgets that tried to inherit from a widget that didn't exist, when the widget is added

This adds a pointer and a bool to Element, which isn't great. It also adds a more or less complete tree walk when you add a new Inherited widget at the top of your tree, which isn't cheap.

...so that people don't think it's for Row.

+ Add new demo to gallery to show data tables. (This currently doesn't
use a Card; I'll create a Card version in a subsequent patch.)

+ Fix checkbox alignment. It now centers in its box regardless.

+ Add Colors.black54.

+ Some minor fixes to dartdocs.

+ DataTable, DataColumn, DataRow, DataCell

+ RowInkWell

+ Augment dartdocs of materia/debug.dart.

+ DropDownButtonHideUnderline to hide the underline in a drop-down when
  used in a DataTable.

+ Add new capabilities to InkResponse to support RowInkWell.

+ Augment dartdocs of materia/material.dart.

+ Add an assert to catch nested Blocks.

+ Fix a crash in RenderBox when you remove an object and an ancestor
  used its baseline. (https://github.com/flutter/flutter/issues/2874)

+ Fix (and redocument) RenderBaseline/Baseline.

+ Add flex support to IntrinsicColumnWidth.

+ Document more stuff on the RenderTable side.

+ Fix a bug with parentData handling on RenderTable children.

+ Completely rewrite the column width computations. The old logic made
  no sense at all.

+ Add dartdocs to widgets/debug.dart.

+ Add a toString for TableRow.

Now past halfway though material.dart by files.

This patch adds a consistent, simple description for the common pattern of
having a single child widget.

This patch renames StatelessComponent to StatelessWidget and
StatefulComponent to StatefulWidget.

Fixes #2308

And fix the zillion issues that uncovered.

This reverts commit f41b3411, reversing
changes made to e33d8d96.

This was a bad check-in due to my mangling uploading a new version of the branch from a different machine.

This reverts https://github.com/flutter/flutter/pull/2639 and will be replaced by https://github.com/flutter/flutter/pull/2640

And fix the zillion issues that uncovered.

Fixes https://github.com/flutter/flutter/issues/2369

The onHighlightChanged callback was being given "true" every time
instead of the actual value.

After this patch, if you try to use a widget that depends on being enclosed in
a material, you now get an assert and a debugPrint if you're not inside a
material.

Fixes #243

Factor out a reusable interface called Decoration from BoxDecoration.

Make all the consumers of BoxDecoration and the erstwhile BoxPainter
into consumers of Decoration.

Make a BoxPainter be something you get from a Decoration, rather than
something to which you pass a BoxDecoration.

Rename Shape to BoxShape now that it's documented specifically as
applying to boxes.

Move EdgeDims to its own file.

Move FractionalOffset up so that it's with the other helper classes in
its file rather than alone at the end.

Minor change to RenderClipOval's hit testing to avoid taking an
unnecessary square root.

Rename BoxDecorationPosition to DecorationPosition since
RenderDecoratedBox now takes any Decoration.

Implement hit testing for rounded rects.

Rename AnimatedBoxDecorationValue to AnimatedDecorationValue, and make
it support lerping across any Decoration (by deferring to the objects
involved).