Right now `utf8.encode()` has a static return type of `List<int>`
due to extending `Encoding` (which extends `Codec<String, List<int>>`).
We cannot easily change `Encoding` to extend `Codec<String, Uint8List>`
because that would also change `utf8.decode()` to require `Uint8List`
which would be a breaking change.
So instead we override `utf8.encode()` to have more precise return type.
Some parts of our SDK are run using the checked-in SDK, so it cannot
rely on the changed return type yet (until checked-in SDK is rolled).
So we use `const Utf8Encoder().convert()` as a temporary change, as
that already has `Uint8List` return type.
Issue https://github.com/dart-lang/sdk/issues/52801
TEST=ci
CoreLibraryReviewExempt: More precise return type for existing API
Change-Id: I2861d1f0eb3d292d8e3ec8437c0d441a2d2bd193
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/254903
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Lasse Nielsen <lrn@google.com>
Martin Kustermann
81df36216f