* Add generated Icon diagram to api docs

* 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

* Added sample code for a simple Icon, ref: #21136

* Removed duplicate line.

* Fixed incoreect parameter.

* Update icon.dart

Removed empty prose and added better context for sample code. Changed sample code for better visibility in execution of default app themes.

* Alas, Trailing space.

Nixed trailing space in comments.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

* lint unnecessary_new on samples

* fix tests

I'm not really sure how to test this without a reference test, since
eventually we want to move this to a font feature and thus the obvious
test (looking for the Transform widget) isn't really valid.

(post-merge followup for #12516)

* Keep Icon's subtree structure the same with and without a semanticLabel.

This avoids rebuilding the subtree when a semanticLabel is set/unset.
Also updated some doc comments.

(This is a followup on post-merge comments for #12475)

* Allow specifying and a11y label for Icon widget

Add Diagnosticable base class and documentation

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

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

* use color.shadeXxx instead of color[Xxx]

* remove calls to .shade500 on MaterialColor

* remove calls to .shade200 on MaterialAccentColor

* fix test

This update adds support for custom fonts in icons. As an example, it
can be used with the icon-set from https://materialdesignicons.com

Thanks to @vlidholt for the original patch.

Fixes #4494
Fixes #3199

Answers http://stackoverflow.com/questions/41729278/why-is-this-icon-being-clipped

Now IconThemeData.fallback is a factory constructor and IconThemeData.of() does
the work of computing the fallback for its clients.

Also, add tests for ImageIcon and ListItems.

Based on observations of usability study participant P1.

This feature is the implementation of an accessibility feature that changes the
size of text by a constant factor.

Fixes #5873

Anywhere that accepted IconData now accepts either an Icon or an
ImageIcon.

Places that used to take an IconData in an `icon` argument, notably
IconButton and DrawerItem, now take a Widget in that slot. You can wrap
the value that used to be passed in in an Icon constructor to get the
same result.

Icon itself now takes the icon as a positional argument, for brevity.

ThemeData now has an iconTheme as well as a primaryIconTheme, the same
way it has had a textTheme and primaryTextTheme for a while.

IconTheme.of() always returns a value now (though that value itself may
have nulls in it). It defaults to the ThemeData.iconTheme.

IconThemeData.fallback() is a new method that returns an icon theme data
structure with all fields filled in.

IconTheme.merge() is a new constructor that takes a context and creates
a widget that mixes in the new values with the inherited values.

Most places that introduced an IconTheme widget now use IconTheme.merge.

IconThemeData.merge and IconThemeData.copyWith act in a way analogous to
the similarly-named members of TextStyle.

ImageIcon is introduced. It acts like Icon but takes an ImageProvider
instead of an IconData.

Also: Fix the analyzer to actually check the stocks app.

As of `1.18.0-dev-0`, these cases will get flagged.  In the meantime, the

Fixes 3544

This patch starts working through the missing dartdocs in widgets.dart.

* Remove IconThemeData.clampedOpacity

+ 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.