This fixes https://github.com/flutter/flutter/issues/39277

The following tests cover this change:
- packages/flutter/test/foundation/service_extensions_test.dart
- packages/flutter/test/scheduler/scheduler_test.dart

* Add structured errors in Animations, TabView, ChangeNotifier

* Add structured error on MaterialPageRoute, BoxBorder, DecorationImagePainter, TextSpan

* Add structured errors in Debug

* Fix test errors

* Add structured errors in Scaffold and Stepper

* Add structured errors in part of Rendering Layer

* Fix failing test due to FloatingPoint precision

* Fix failing tests due to precision error and not using final

* Fix failing test due to floating precision error with RegEx instead

* Add structured error in CustomLayout and increase test coverage

* Add structured error & its test in ListBody

* Add structured error in ProxyBox and increase test coverage

* Add structured error message in Viewport

* Fix styles and add more assertions on ErrorHint and DiagnosticProperty

* Add structured error in scheduler/binding and scheduler/ticker
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured error in AssetBundle and TextInput
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured errors in several widgets #1
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Remove unused import
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add assertions on hint messages
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Fix catch spacing
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured error in several widgets part 2 and increase code coverage
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Add structured error in flutter_test/widget_tester

* Fix floating precision accuracy by using RegExp
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Remove todo to add tests in Scaffold showBottomSheet
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Fix reviews by indenting lines and fixing the assertion orders
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Fix failing tests due to renaming class
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Try skipping the NetworkBundleTest
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

* Remove leading space in material/debug error hint
Signed-off-by: Albertus Angga Raharja <albertusangga@google.com>

This changes the DropDownButton so that instead of dismissing itself when any metrics change occurs, it only dismisses itself when the orientation changes.

This gets around the fact that we can't currently have a dropdown and a text field on the same page because the keyboard disappearing when the dropdown gets focus causes a metrics change, and the dropdown immediately disappears when activated.

It still will cause the keyboard to jump up and down between controls, but that's a larger issue. At least now we can use the two together again.

* Implement system fonts system channel listener

This reverts commit 6ef80b44.

This is the continuation of https://github.com/flutter/engine/pull/11041 and https://github.com/flutter/flutter/pull/38574

This is not a breaking change as we're not removing `onReportTimings` API.
We're simply removing the use of it in our framework.

* Moved the default BinaryMessenger instance to ServicesBinding

This reverts commit 821602ae.

* Added assertion in defaultBinaryMessenger. Also fixed the devicelab tests.

Filed: https://github.com/flutter/flutter/issues/38838
to track these usages.

This was introduced by: https://github.com/flutter/engine/pull/11041

This reverts commit 92ef2b9c.

This requires either runApp() or
WidgetsFlutterBinding.ensureInitialized() to have been called before
using any MethodChannels. Plugins broadly rely on MethodChannels and
right now there's no general requirements that they be constructed
within the runApp call, so the ecosystem breakages from this are broader
than originally thought. Reverting for now.

TimelineEvents may not be sent if there aren't enough to form a group.
Hence we should always use ExtensionEvent as the trigger.

See also https://github.com/flutter/flutter/pull/37503

The hack here is to flush the timeline events so the host that
waits for the 'Rasterized first useful frame' event won't hang.
Previously 'Widgets built first useful frame' didn't cause this
trouble because the GPU thread will naturally add more events later
and cause a fresh. The `Rasterized...` event, however, is likely
to be the last (or nearly the last) event during the app start up.

rmacnak and I will figure out a better way to fix it next week.
We're having this quick hack now to fix our device lab performance
tests so we won't miss the data points.

This relands https://github.com/flutter/flutter/pull/35297

The followings have been done to fix the broken tests:
  1. Add `didSendFirstFrameRasterizedEvent` extension and its tests
  2. Wait for `didSendFirstFrameRasterizedEvent` instead of
     `didSendFirstFrameEvent` during start up tests
  3. Mark missed (probably newly added) start up tests as flaky

This reverts commit 68fc7231.

This should fix https://github.com/flutter/flutter/issues/31442 and https://github.com/flutter/flutter/issues/34867

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

This re-applies #32437 with a fix to the broken device lab test.

This reverts commit 069303d4.

Make FlutterError objects more structured so they can be displayed better in debugging tools such as Dart DevTools.

## Description

Previously, such function is only available in the debug mode. But the
performance information is very noisy in debug mode with JIT. I feel
that such function is as important and useful as the performance overlay
and the `--trace-skia` option for the GPU thread.  So we should give it
the same ability to run in both profile and debug mode.

I've tested it using flutter_gallery in the profile mode. There's no
observable difference in the performance overlay between toggling widget
build profiling.

## Related Issues

https://github.com/flutter/flutter/issues/30984

* add trailing commas on list/map/parameters

* add trailing commas on Invocation with nb of arg>1

* add commas for widget containing widgets

* add trailing commas if instantiation contains trailing comma

* revert bad change

Fix the spelling errors in the dartdocs for the framework.

There are no functionality changes here, just documentation fixes.

These are essentially self-inflicted race conditions. Instead of timeouts we're going to try a more verbose logging mechanism that points out when things are taking a long time.

* Add didSendFirstFrameEvent service extension.

New locale resolution algorithm to use full preferred locale list, include scriptCode in Locale. (#23583)

This converts existing ## Sample code samples to {@tool sample}...{@end-tool} form.

Also:
1. Fixed a minor bug in analyze-sample-code.dart
2. Made the snippet tool only insert descriptions if the description is non-empty.
3. Moved the Card diagram to before the code sample.