For G3 Roll:
* Revert "MaterialButton must honor its minWidth and height parameters (#22919)"
This reverts commit a02332335a.
* Revert "Update uses of ButtonTheme.bar: pass along the current Theme's colorScheme (#22827)"
This reverts commit 655bf6a290.
* Revert "ButtonTheme.of().colorScheme defers to Theme (#22880)"
This reverts commit a590940e45.
* Revert "Bring TextTheme into alignment with the current Material spec (#22330)"
This reverts commit 8bfb4b3ee5.
* Revert "Added ColorScheme, updated ThemeData, ButtonTheme, material buttons (#22013)"
This reverts commit eea3465ae7.
* Manual adjustments to fix reversion issues.
The following changes are made by this PR:
* Translation bundles now implement MaterialLocalizations directly,
and are public so that they can be directly extended.
* The list of supported languages is now a generated constant.
* The icuShortTimePattern/TimeOfDayFormat values are now pre-parsed.
* Various other changes for consistency with the style guide and the
rest of the codebase, e.g. the class names don't use `_`, the
`path` library is imported as such, more dartdocs, fewer `//
ignore`s, validation using exceptions.
This reduces our technical debt benchmark.
* 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)
```
