UnconstrainedBox will allow its child to size itself as if it had no constraints, and then attempt to fit around that object, until its own constraints are exceeded, in which case it will clip and display an overflow warning.

I also factored out DebugOverflowIndicator, which will draw overflow indicators on containers which overflow but aren't expected to.

* fix with first part of test

* Test without reshifting

* Let sliver fixed extend list also handle disappearing top items.

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.

* address unused element issues and new warnings

* add a missing return

* enable lint prefer_asserts_in_initializer_lists

* enable --assert-initializer

* a => an

(I suspect this accounts the sets of microtasks from scheduleWarmUpFrame now running separately.)

Issue https://github.com/flutter/flutter/issues/9998

* Surface shadowColor from RenderPhysicalModel to Material

* Fix typo in material_test

* Add nullability info to documentation

* Add support for animating elevation shadow color

* Add shadowColor to Material's debugFillProperties()

* Add missing default value for elevation in Material debugFillProperties()

* Add missing non-null asserts for animate flags in AnimatedPhysicalModel

* Add test for shadow color animating smoothly

* delay taking screenshot to allow GPU thread to render the frame

* address comments

Since MethodCall equality checks are limited to test scenarios, this
patch replaces them with an equivalent test matcher. At present
MethodCalls are always used in scenarios where indentity-based
equality/hashing is appropriate.

This change avoids an assertion failure when MethodCall args are
Iterable (possible since args are of type dyanmic), and hashValue() from
dart:ui asserts that its input is not an Iterable.

The alternative of implementing support for deep equality in dart:ui was
rejected on the basis that if we're to encourage performant code,
expensive checks should be obviously-expensive to the author.

There was a left-bias when MainAxisSize.min couldn't be honoured.

* Leave a version tag when creating project

* Generalize .version to .metadata

Use TextPainter.preferredLineHeight to estimate line height for Cupertino selection handles (#12833)

Fixes https://github.com/flutter/flutter/issues/12046

* Built first tab

* Small additions

* started tab 3

* Need color arithmetics

* tab 2 built

* finalize

* lint and tests

* review

* Reapply docs after rebase

* use color.computeLuminance

* linter

* nit

* remove extracted methods

* lint

* make microbenchmark logging verbose

* prefix JSON so it can be parsed in verbose mode

This fixes the assumption that InputDecorator had where it expected baseStyle to be a complete style. Now it merges the baseStyle with the subhead style instead of substituting it entirely.

This fixes #12832.