Fixes #7119

The Ahem font has a much wider average text width than most fonts.

Now that ensureVisible works, we can use ListView instead of Block in
this demo.

* improve the logger ui a bit for elapsed times

* invert param

* update daemon.dart

Also, switch Stepper over to using sliver-based scrolling.

Differentiate between the not-installed and the out-of-date scenario.

Call `pub upgrade` instead of manually deleting `pubspec.lock` and then calling `pub get`. `pub upgrade` ignores the `pubspec.lock`, but is otherwise identically to 'pub get' (https://www.dartlang.org/tools/pub/cmd/pub-upgrade).

Add a user friendly error message when no development team is selected for physical deployment (#7879)

Bump to keep up w/ DDC fixes.

Support for thinning app frameworks to the target architecture was added
in 708909fc. This commit adds support
and error-checking for non-fat frameworks that are not of the target
architecture. In such cases, we now fail the build, and emit an error
message and the contents of lipo -info for the affected framework.

This patch improves PageView to the point where we can use it in the date
picker. Specifically, you now get onPageChanged notifications and you can
control which page is visible using a PageController.

There appears to be an issue with children before the center widget.
I've filled a bug about that issue and will follow up in a later patch.

We need to study these benchmark numbers more carefully. See #7937

Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant. (#7944)

* Add find.descendant API to support find descendants of an element by passing the current element and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Add find.descendant API to support find descendants of an element by passing the current element finder and the finder of descendant.

* Support thinning iOS frameworks to supported architectures

When building against frameworks that are distributed as
multi-architecture fat binaries, we want to strip the frameworks we
distribute down to only the architectures specified in $ARCHS.

This patch adds:
* The ability to specify commands to xcode_backend.sh (if none is
  specified, run BuildApp for backward compatibility).
* A 'thin' command that invokes lipo to thin down the distributed as
  described above.

* Add framework thinning step to iOS build

Invokes xcode_backend.sh thin on the build application.

* Limit architectures to arm64 in Xcode template

Flutter does not yet support armv7 iOS devices. Limit the $ARCHS build
variable to arm64 until then.

* has all the cherry-picks fixing known issues merged.

Also, move the creation of the ScrollPosition to ScrollController.

Finally, remove TestScrollable in favor of CustomScrollView, which is the
production version of this widget.

If you pass a ScrollController to a Scrollable2, you can use the controller to
read and write the scroll offset without having to find the Scrollable2State
object.

Reason: https://github.com/flutter/flutter/issues/4273

In particular, we now use ListView in the about dialog.

Required to run tests on Windows bots.

These arguments are actually required because we assert that they're not null.

These widget don't have any clients anymore. Consider using GridView instead.

* Small Flutter strong mode cleanup fixes.

These are cases where strong mode down cast composite errors
generally indicated cases that would performance or correctness
issues if Flutter code was run in a strong mode VM.

* Fix Command API so that it is always in terms of Map<String,String>.

* Fix typedef