Fix the spelling errors in the dartdocs for the engine.

There are no functionality changes here, just documentation fixes.

The defaultClipBehavior is no longer used anywhere in the Flutter framework and Google3.

Most changes are trivial except pushTransform. In pushTransform, matrix4 is an Dart object and it has to be released before we can return a new Dart object (EngineLayer).

* Add missing entry-points.

* Fix lint

See https://github.com/flutter/flutter/pull/22566#discussion_r226082171
for why we add this.

This will be used for embedding UIViews on iOS.

Landing a no-op layer as a first incremental step to keep PRs small.

This reverts commit 74662ab6.

This should land after https://github.com/flutter/engine/pull/6442

* Add pragma vm:entry-point

Otherwise, an object may be both null and an instance of EnginieLayer at
the same time in Dart.

Reverts flutter/engine#6406

We need to fix the SkiaGPUObject issue of the raster cache SkImage before merging this PR.

To make the PR minimal, we currently only share the engine layer when `pushPhysicalShape` (for Fuchsia) or `pushOffset` (for `RepaintBoundary` and `Opacity`) are called. They should be sufficient for our short-term perf goal. In the future, we can incrementally share more engine layers with the framework.

https://github.com/flutter/flutter/issues/21756

For https://github.com/flutter/flutter/pull/21619#discussion_r220390088

The `dart_vm_entry_points.txt` file is now deprecated in favor of annotations.
Support for parsing and generating the entry-points files will be removed from Dart shortly.

This is a follow up of https://github.com/flutter/engine/pull/5853

This is needed to avoid jank when resizing an embedded Android view.
See
https://github.com/flutter/flutter/issues/19572#issuecomment-410400724

The is a follow up of https://github.com/flutter/engine/pull/5853

For flutter/flutter#18057

So our future pull requests won't be polluted by the white space changes.

* pass shadow_color from dart:ui to physical layer

* default shadow color to SK_ColorBLACK

* add doc comments to pushPhysicalShape

* Make native wrapper classes non-abstract as they are instantiated from native code
* Make constructors of native wrapper classes private

* Analysis cleanup of the Dart in the Engine repo

* Update painting.dart

* Update painting.dart

This reverts commit d8740c70.

* Adjust PhysicalModelLayer to use an abstract shape, and provide concrete RRect and Path shape implementations

* add a pushPhysicalShape to scene_builder and compositing.dart

These libraries are in Topaz now.

Now it references dart:zircon and dart:fuchsia.

* Update to new Dart FIDL bindings API.

Compute the necessary texture resolution using more accurate scaling
information provided by Mozart scene node metrics events instead of the
device pixel ratio provided by the Mozart view properties (which we
might remove in the future).

This allows us to allocate smaller textures when a Flutter view is
being scaled down.

Fixes https://github.com/flutter/flutter/issues/9473

This name is consistent with how the other `dart:` libraries are named now.

Fixes https://github.com/flutter/flutter/issues/7200