This reverts commit d200dc15.

This adds an example of how to move to the "next" field when using TextInputAction.next. This is all that is needed to have "next field" functionality in a field. I thought about making it the default when handling the "next" or "previous" actions, but it's better that the developer has control over whether or not they actually move to the next field, and within which scope.

https://github.com/flutter/engine/compare/75387dbc147d...49445ce4949b

git log 75387dbc147d1cee8164f5d61582eab8ba1e5058..49445ce4949bf0d28506a6b22e28b4264f624e5f --no-merges --oneline
49445ce49 FLEViewController/Engine API changes (flutter/engine#9750)
2a79462fd Add Fuchsia build CI presubmit steps (flutter/engine#9736)
67cebdb92 Roll fuchsia/sdk/core/linux-amd64 from KGmm_RIJoXS19zTm2crjM3RYpmp5Y03-fLUeVdylbTYC to ehWVT9QJbC-vFMM6SkkQM9HJ9oITFCws7FC9JnrFq2gC (flutter/engine#9765)
089c74084 Roll fuchsia/sdk/core/mac-amd64 from lCQWEeR_Ert7t_qAbMRycwrRyZC-dIprYPyPJzwPmg4C to EYnRdXFT9l-d8Qkz4zeTRXnqfV3KQzpQhoPs1r0-740C (flutter/engine#9759)
b22410ef6 Include SkParagraph headers only when the enable-skshaper flag is on (flutter/engine#9758)
2cd650d26 Minimal integration with the Skia text shaper module (flutter/engine#9556)
f775f5e4d Re-enable the Wuffs GIF decoder (flutter/engine#9466)
aca048236 Make all shell unit tests use the OpenGL rasterizer. (flutter/engine#9746)
bc57291ff Make FLEViewController's view an internal detail (flutter/engine#9741)
9776043ea Synchronize main thread and gpu thread for first render frame (flutter/engine#9506)
f600ae830 Use libc++ variant of string view and remove the FML variant. (flutter/engine#9737)
564f53f0a Revert "Improve caching limits for Skia (#9503)" (flutter/engine#9740)
b453d3c3d libtxt: fix reference counting of SkFontStyleSets held by font asset providers (flutter/engine#9561)
fa7627d17 Fix backspace crash on Chinese devices (flutter/engine#9734)
56885f79b Let pushColorFilter accept all types of ColorFilters (flutter/engine#9641)
6dccb21e6 Roll src/third_party/skia 96fdfe0fe88e..af4e7b6cf616 (1 commits) (flutter/engine#9735)
8511d9b47 Roll fuchsia/sdk/core/mac-amd64 from byM-kyxL4bemlTYNqhKUfJfZoIUrCSzS6XzsFr4n9-MC to lCQWEeR_Ert7t_qAbMRycwrRyZC-dIprYPyPJzwPmg4C (flutter/engine#9742)
b3bf0a182 Roll fuchsia/sdk/core/linux-amd64 from I2Qe1zxgckzIzMBTztvzeWYsDgcb9Fw-idSI16oIlx8C to KGmm_RIJoXS19zTm2crjM3RYpmp5Y03-fLUeVdylbTYC (flutter/engine#9743)
7e568232a Fix windows test by not attempting to open a directory as a file. (flutter/engine#9745)
6cf0d1350 Roll src/third_party/skia a3ffaabcc4f2..96fdfe0fe88e (5 commits) (flutter/engine#9731)
49a00aed8 Fix Fuchsia build. (flutter/engine#9730)
b3bb39b0b Roll src/third_party/dart 06c3d7ad3a...09fc76bc51 (flutter/engine#9728)
2284210f4 Make the license script compatible with recently changed Dart I/O stream APIs (flutter/engine#9725)
ad582b508 Rework image & texture management to use concurrent message queues. (flutter/engine#9486)
1dcd5f52b Roll src/third_party/skia 6b82cf638682..a3ffaabcc4f2 (24 commits) (flutter/engine#9726)
129979cab Revert "Roll src/third_party/dart 06c3d7ad3a..7acecda2cc (12 commits)" (flutter/engine#9724)
8020d7e43 Roll src/third_party/skia 56065d9b875f..6b82cf638682 (3 commits) (flutter/engine#9718)
e24bd7846 Roll src/third_party/dart 06c3d7ad3a..7acecda2cc (12 commits)
3d2668c35 Reland isolate group changes
802bd1518 iOS platform view opacity (flutter/engine#9667)
3b6265b74 Roll src/third_party/dart b5aeaa6796..06c3d7ad3a (44 commits)
887e05233 Refactor ColorFilter to have a native wrapper (flutter/engine#9668)

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Change focus example to be more canonical (and correct), listening to the focus node for changes. (#35913)

This changes the example for FocusNode to be more correct, listening to the focus node for changes, instead of assuming that it is the only one doing the changing.

This adds an "anchor button" to each of the samples so that the user can link to individual samples instead of having to link to just the page. Clicking on the anchor button jumps to the anchor, as well as copying the anchor URL to the clipboard.

There is some oddness in the implementation: because dartdoc uses a <base> tag, the href for the link can't just be "#id", it has to calculate the URL from the current window href. I do that in the onmouseenter and onclick because onload doesn't get triggered for <a> tags (and onmouseenter doesn't get triggered for mobile platforms), but I still want the href to be updated before someone right-clicks it to copy the URL.

Show and hide the text selection menu at the correct time with various gestures in the text field.

* Remove extra classes.

Now that https://github.com/dart-lang/sdk/issues/31543 is fixed, we
can remove extra classes.

* Add snapConfiguration to parameters for _RenderSliverFloatingPersistentHeaderForWidgets and _RenderSliverFloatingPinnedPersistentHeaderForWidgets constructors.

Fixed build of example code to use new binary messenger API.

* Add flag to use root navigator for showModalBottomSheet

* Add documentation

* Add tests

* Address feedback and fix analyzer issues

* Address feedback

* Update comments

* Fixed assets embedding

* ++

* Completed snippet audit

* Analyzer

This introduces a script that implements the conventions described in https://github.com/flutter/tests/pull/1.

* Add Colors.white38

* Update ThemeData.disabledColor and ButtonThemeData.disabledColor to Colors.white38

* Update pre-existing tests to expect Colors.white38 instead of Colors.white30

* Update API documentation to reflect these changes

When I added reverseDuration to animation controllers in #32730, I also added it to the implicit animations that Flutter has. However, as @efortuna pointed out to me, it doesn't actually do anything there, since all of the intrinsic animations run forwards, not in the reverse direction, and there's no way to reverse them.

So, this PR removes the reverseDuration argument from the implicit animations to avoid confusion.

Fixes #35769

* add sample code for AnimatedContainer

* use stateful_widget_scaffold snippet template

* add sample explanation

* add setState() to example assumptions for analyzer

* update description

* use snippet instead of sample

* change sample to match assets-for-api-docs

* remove constant

* update AnimatedContainer sample description

add indication the example is depicted by the video and animates when
tapped

* fix example formatting

* make sample conform to 80 col limit

* add "implemented below" to illustration description

* formatting for readability

Added support for a themeMode property to the MaterialApp to control
how the light or dark theme is selected.

[Material] Text scale and wide label fixes for Slider and Range Slider value indicator shape (#35496)

Various bug fixes for Slider and Range Slider value indicator around accessibility and wide labels.

Rendering errors with root causes in the widget layer should have a reference to the widget (#32511)

* Initial work

* ++

* Updated tests

* Moved TestObserver out for access across tests.

* ++

* Added hero tests

* Review feedback

* simplified preceding route overlay

* Review feedback

* trailing doc slash

* Add missing [applicationIcon] property to LicensePage widget

For https://github.com/flutter/flutter/issues/31086.

Also test if our mac8 with iPhone XS is working
(https://github.com/flutter/flutter/issues/34590).