These futures complete when the route is popped off the navigator. This
generalizes and simplifies a mechanism already in place for dialogs and
menus.

Fixes #5283

When not dismissing, the Dismissable widget should cull its background.
When a dismiss is in progress, it should clip the background to just the
part that is revealed.

Fixes #6127

Previously we assumed the dial was square, which isn't always the case.

Fixes #6315

I added some documentation to Input as I was learning how it worked
(and some minor tweaks, like handling reparenting better).

* Add a maxLines parameter for multiline Input.

If maxLines is 1, it's a single line Input that scrolls horizontally.
Otherwise, overflowed text wraps and scrolls vertically, taking up at
most `maxLines`.

Also fixed scrolling behavior so that the Input scrolls ensuring the
cursor is always visible.

Fixes https://github.com/flutter/flutter/issues/6271

* oops

* comments

* import

* test and RO.update fix

* constant

* fix.caretRect

Instead, we now interact with the system navigator via SystemNavigator.

Previously, if you focused a field, fields below it would shift down by one pixel.

This change tries to guarantee that that won't happen.

We weren't computing the bounds for composited transforms correctly. We
need to conjugate the transform by the offset in order to get the
correct paint bounds for the composited layer. We now also use the same
math in the non-composited case for consistency.

Also, don't scale the z-coordinate in RenderFittedBox.

Fixes #6293

* Switch to using PlatformPlugin instead of mojom

* Update engine.version

The Skia team tells us that these go faster.

This wrapper will eventually replace HostMessages.

We were missing these before.

This match switches the framework to use the semantics backend in `dart:ui`
rather than the Mojo backend.

Instead of reading the mojom serialization and re-inflating it, the
SemanticsDebugger now shows the SemanticsNode objects directly.

Performance improvement for https://github.com/flutter/flutter/issues/6008

This patch adds `@checked` everywhere is needed to remove the
`strong_mode_invalid_method_override` strong mode error.

This will make it easier to switch to SemanticsUpdateBuilder.

This change might make our grammar less perfect, but it will increase our
sanity.

Fixes https://github.com/flutter/flutter/issues/5763

Fixes https://github.com/flutter/flutter/issues/6154

Fixes #6215

* Bump Dart SDK to `1.20.0-dev.10.0`.

`1.20.0-dev.10.0` corresponds to `1.20-RC0`.

* pubspec.lock cleanup

* check for pubspec.lock existence

* cleaned up conditional remove

This widget now lives in Mozart:

https://fuchsia.googlesource.com/mozart/+/master/lib/flutter/child_view.dart

This patch removes the Mozart dependencies from object.dart and
layer.dart, which will make it easier for us to move the Mozart
dependencies purely into the Fuchsia tree.

Fixes #988

Fixes https://github.com/flutter/flutter/issues/4478

DragTarget would call setState after it was disposed in didLeave
and didDrop. Fixes #6128.

Now dart:ui does the decoding of the pointer data itself, which means we don't
need to do it in the framework.

Fixes #5141

Rather than removing all the padding from an AlertDialog, we now just use
Dialog directly for the date picker.

To match the Align widget (and several other widgets).

Fixes #6101