Kevin Lubick 46d1954049 Reland image encoder (flutter/engine#41632)
This is a reland of #41368 with fix for transparent images and a unit
test to verify it.

Skia would like to remove `SkImageGenerator::MakeFromEncoded` and this
appears to be the only remaining usage. It appears to be easily swapped
out for the `SkImages::DeferredFromEncodedData`. (skbug.com/13052)

This also removes the use of the internal `SkCodecImageGenerator` for
the public `SkCodec` API (which the image generator had just been
deferring to anyway).

While unbreaking some unit tests, I made a few assertions easier to
debug and produce nicer error messages.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making or feature I am
adding, or Hixie said the PR is test-exempt. See [testing the engine]
for instructions on writing and running engine tests.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I signed the [CLA].
- [ ] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo
[C++, Objective-C, Java style guides]:
https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style
[testing the engine]:
https://github.com/flutter/flutter/wiki/Testing-the-engine
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#handling-breaking-changes
[Discord]: https://github.com/flutter/flutter/wiki/Chat
2023-05-01 07:33:23 -07:00
Languages
Dart 75%
C++ 16.5%
Objective-C++ 2.9%
Java 2.8%
Objective-C 0.7%
Other 1.9%