* [web canvaskit] fix SkiaObjectBox instrumentation

* WIP add text crash test

* Add failing test

This reverts commit b3ebb6dd.

See: https://github.com/flutter/flutter/issues/83753

* delete paragraphs between layout and render

This reverts commit 78f5dde9.

* If CanvasKit has already been initialized, don't load it again.

This could be useful for hot restart or for DartPad.

* Don't redownload script if it is already loaded.

* trailing whitespace

* Touch up comments

In each library where an import is removed, the library uses some elements
provided by the import, BUT there is another import which provides all of the
same elements, and at least one more which the library uses.

In this change, we remove the imports which can be simply removed in favor of
the other already present imports.

See https://github.com/dart-lang/sdk/issues/44569 for more information.

* fix race with framework when using tab to traverse in a11y mode

It broke an integration test on the framework side.

This reverts commit aa2672ff.

* auto-enable semantics

* fix a11y placeholder on desktop