No code changes, just comments: I spell-checked all the comments in the repo.

This adds support for the command key for text selection/editing on macOS. I had ported the text editing code (in #42879), but forgot to add support for the command key itself. This also adds a test that tests the text editing on multiple platforms instead of just testing Android.

There appears to still be a bug (filed #44135) where we're losing key events sometimes on macOS, leaving some keys "stuck" on, but this PR at least allows the right key combinations to be used.

Convert the call to getWordBoundary to use a TextPosition, in preparation for landing flutter/engine#13727, which switches the desired API to the final desired API.

This removes TextRange from the framework and moves it to the engine, in preparation for using it to return text ranges from the text extent APIs, and updates the APIs that use Paragraph.getWordBoundary (there was only one) to expect a TextRange or  a pair of ints temporarily until the engine side returns TextRanges, so that I can convert over without breaking the builds.

* 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>

* Implement system fonts system channel listener

This reverts commit b12bdd0e as it
breaks existing tests that expect image loaded after certaing number of
pupms. With image loading done on separate isolate pumping is not
guaranteed to get image loaded.

* Use separate isolate for image loading. Use TransferableTypedData to const-cost receive bytes from that isolate.

* Minor improvements to framework documentation.

* maybePop documentation fix

* Mark some flutter_test arguments required.

Without these set, we get a crash.

* Minor correction to ListView docs

Docs improvement after seeing "null" showing up for TextWidthBasis.

This reverts commit d67f47b2.

This reverts commit ddd31bce.

The update is copied from an update we made to a Google-internal
client: cl/260202900

The update will save 1 shader compilation.

This should help solve our regression:
https://github.com/flutter/flutter/issues/31203

More regressions on iOS might be introduced later by
https://github.com/flutter/engine/pull/9813#issuecomment-520039890

Unfortunately, we didn't rebase our benchmarks so such regressions
were not detected.

Hence to fully solve https://github.com/flutter/flutter/issues/31203,
we might need to revert some change in
https://github.com/flutter/engine/pull/9813 to make iOS shader warm-up
happen on the GPU thread again.

Primarily these methods no longer allocate any objects other than their
return values.

Additionally, the math in the methods is reduced compared to the general
case math based on known input conditions.

Modified to no longer generate infinite values in some finite cases.

* Revert "Optimize the transformRect and transformPoint methods in matrix_utils. (#36396)"

This reverts commit 9946f7cf.

* add test

Sped up shader warmup by only drawing on a 100x100 surface and doing
the draw calls on top of each other.

Primarily these methods no longer allocate any objects other than their
return values.

Additionally, the math in the methods is reduced compared to the general
case math based on known input conditions.