* 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

* Use uris for hot reload invalidation.

* Clean up unneccessary conversions

* add final.

* Revert sample change

This is follow-up to https://github.com/flutter/flutter/pull/15537 to make dart1 coverage test happy.

* a11y: remove SemanticsSortOrder; sort locally only; semanticsOwner post-test check

* update accessibility test framework

- default nextNodeId/previousNodeId to -1
- stop treating null as opt-out from value testing
- add `id`, `TestSemantics.root`, and `tags` to the suggested code in the TestSemantics failure message
- fix a small bug with raw string escaping
- update all tests accordingly

* fix sortKey doc

* prefer const over final

Fixes https://github.com/flutter/flutter/issues/15410

* Revert "Revert "Reland pass filesystem options (#15622)" (#15651)"

This reverts commit 0f3eada0.

* Fix for windows failing test

* !isEmpty -> isNotEmpty

* fail ios workflow when simctl does not work

* missed rename commit

* address comments

Includes:
* Roll Dart to f1ebe2bd5cfcb6b522e5b4fd406cdabb1a2d2091. (#4805)

This reverts commit bbcf55a5 as it breaks hot reload on Windows.

* Revert "Revert "Pass filesystem-root, filesystem-scheme options through `flutter run, build` and gradle. (#15592)" (#15621)"

This reverts commit c663e336.

* Check whether filesystem-root is emtpy.

* Restore broken merge

* Fix windows test

* Adjust regex in test. Invalidate files by file path.

Includes:
* [fuchsia] Updated scenic fidl prefix (flutter/engine#4798)
* Cache render buffer extents when no depth/stencil buffer (flutter/engine#4801)
* Eliminate iOS depth/stencil buffer code (flutter/engine#4802)
* [fuchsia] Adapt to FIDL1 VectorPtr API (flutter/engine#4804)

Includes:
* Provide lookup key to access Flutter assets in the APK (flutter/engine#4785)
* Roll skia and update licenses (flutter/engine#4797)
* libtxt: retain hard line breaks when calculating maxIntrinsicWidth (flutter/engine#4796)

Running test coverage in dart2 mode runs over allocated timeslot on bots.

* Fix strong mode error in platform_channel/main.dart

* Addres code review comments.

Revert "Pass filesystem-root, filesystem-scheme options through `flutter run, build` and gradle. (#15592)" (#15621)

This reverts commit 0f659fb1 as it
breaks bin/tasks/gradle_plugin_test.dart.

* Pass filesystem-root, filesystem-scheme options through flutter run/build/gradle.

Fixes https://github.com/flutter/flutter/issues/15037

Get to green build.