This updates the visual look of the Chip class, so that it scales properly in the face of text scale (and label widget size) changes, and bases its height off of the label widget's height, constraining the other widgets it contains to be the same height.

To do this properly, I had to implement a custom render object that will measure the height of the label, so the guts of this class are basically rewritten.

In addition, to allow the circle avatar to increase in size when the chip does, I added minRadius and maxRadius arguments to it, and I updated its color handling to use the light/dark primary colors of the theme in a smart way instead of just using black and white.

Updated and added tests.

* Gallery scaffolding

* Started RenderSliver

* demo and initial hookup

* Cleaned up demo more and scaffolding basic sliver->widget communication structure.

* works

* states and default indicator building works

* start adding docs

* added an alignment setting optimized the sliver relayout mechanism

* tested a default bottom aligned sized indicator

* Added a bunch of tests

* more fixes and more tests

* Finished the tests

* Add docs

* Add more doc diffing wrt material pull to refresh

* Mention nav bar synergy

* add more asserts

* review 1

* Fix mockito 2 / dart 2 / strong typed tests

* review

* Remove the vscode config

* review

* Add more docs and examples for implementers of RenderSliver

* add more typical scenarios to describe scrollOffset

* review

* tweak a word

Also adds test for interpolating gradient stops.

* pass shadowColor param to SceneBuilder

* add doc comment and diagnostic node for shadowColor

* Add missing shadowColor param

* traverse dependencies and dev dependencies separately

* separate dev and reg deps

* update pubspecs

* add checksum string and update transitive dep string.  Add additional verify command to check checksum

* cleanup comments

* add missing space, quote, run verify-onlu from bot script

* rerun tool with fixed string

* ensure correct working directory and bump versions

* flutter not flutterRoot

See https://help.github.com/articles/licensing-a-repository/#detecting-a-license

* Report an error if compilation times out instead of waiting forever.

* Remove braces

* roll engine version to 6280adbfb1f9f63cdc6179b9b78634add1e4f2e3

* Correctly handle previewDart : false setting in AnalysisServer and
AnalyzeOnce classes.

* Support password fields for a11y

* rename to obscured

* Roll engine to c3ab0c9143029f0267a05b99effbfbd280a4901b

Add another rel device to isLocalEmulator to make working flutter run --release

* rotate expansion icon fully if initial state expanded = true

* add test case for initially expanded

* remove unused import

* Update expand_icon_test.dart

add linebreak

* import dart:math as math

* Add a way to generically go back on both Material and Cupertino scaffold pages

* review

* lint

* review

* Fix text assert text

Fixes #7032

This adds a slider demo with a custom theme to the gallery.

In the process of adding this, I decided to add a text theme to the SliderThemeData, since it's a pain to change the text style on the value indicator otherwise.

This reverts commit c8fd99fb.

* With dart being default, move preview_dart_2 tests to dart1.

* Swap out defaults for preview-dart-2 option in tests. Make dart1 explicit

* Move suffix around

* Rename files

Fixes https://github.com/flutter/flutter/issues/15361