* replace child parameter with builder on showDialog

* change builder parameter to WidgetBuilder

* mark child as deprecated and expand documentation to cover this and how builder should be used

* tidy comments and address some feedback

* phrasing

* move space to prev line and add //ignore comments for deprecated member use

* address comments and fix it's its

* update code samples

* adds semicolon to code snippets

* change ThemeData.primaryColor to PrimarySwatch instead of PrimarySwatch[500]

* fix mismatched color in stock test case

This engine has libtxt enabled by default

This change makes the discrete slider show the value indicator for a minimum amount of time for any interaction (tap, drag).

During the review, we determined that it would be good for the value indicator to stretch when the text scale was smaller, and the shrink when it was larger, to keep the value visible over the finger at small sizes, and closer to the finger at large sizes. This implements that change.

Avoids a null pointer exception if dispose() is called on an
already-disposed InkDecoration.

This fixes https://github.com/flutter/flutter/issues/15458.

* Use a set to remove duplicate channel names

* Add test for git command

* Roll engine to b6df7a637498ca9beda1fa9cd7210e3202ea599f.

Changes since last roll:
```
b6df7a637 Roll dart to 290c576264faa096a0b3206c71b2435309d9f904. (#4771)
a6764dbd5 Add sources for Fuchsia target. (#4763)
2d5900615 [fuchsia] Remove unused header file. (#4769)
9717063b7 Revert "Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)" (#4768)
9a9814312 Roll dart to c080951d45e79cd25df98036c4be835b284a269c. (#4767)
e74e8b35c [async] Update includes of async headers to new path (#4760)
e2c4b2760 Use Dart 2 camel case constants in the engine Dart libraries (#4766)
9c1e48434 Updates for Fuchsia roll. (#4765)
14c940e27 Switch from fxl::Mutex to std::mutex (#4764)
debf82c0b Roll Garnet (#4759)
5bffdefbb Use weak pointers to the accesibility bridge from objects vended to the UIKit accessibility framework. (#4761)
```

* Silence broken test

* Mark test as flaky instead

Plus run_machine_concurrent_hot_reload which isn't all green, but is
green since the fix was pushed.

* Update the following packages
- dart-petitparser to 1.7.5
- dart-xml to 3.0.3
- image to 1.1.30
These updates fix some of the strong mode errors we were encountering
while running flutter tests.

This allows other code to get the same style without having to know exactly it is computed.

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

This fixes the error handling for the packaging script so that it will properly report a failure exit code when it can't find the executable that it's looking for.

Added a test too.

See https://github.com/flutter/flutter/commit/3961306badd313a3f34c5c25a754c1e53a581caf

Fixed the real repaint problem the Slider had (missing addListener), and added tests for it.

Added GlobalKey reparenting test.

Added the ability for the value indicator to slide left and right to avoid falling off the edge of the screen.
It only shifts as much as it can without deforming, but even at large text scales, that is enough to keep the text on the screen.

Updated the formatting on theme_data.dart and others to use longer line length.

Also, removed a color tween that faded the value indicator in as it scaled, since that wasn't to spec.

Fixes https://github.com/flutter/flutter/issues/12445

* Update dependencies with forced upgrade.

Now that https://github.com/flutter/flutter/issues/15261 is fixed, do the update with upgrade.

* Update test package use following upgrade

* Replace addOption(allowMultiple) with addMultiOption

* add fromSpan constructor to Text widget and simple smoke test:

* change fromSpan to rich, clean up comments

* 'directly from' to 'with'

* make sure text styles are applied to either data or textspan. add diagnostic properties for span

* add expectation for text style to test case

* some work on diagnostics and docs