* Exclude flutter_goldens package from dartdoc because it's for internal
use only
* Document why flutter_tools doesn' tneed to be excluded from the list of
packages to document
* Performance optimization in the flutter comparator, and associated
test updates.
In order to avoid checking binaries into flutter/flutter,
this comparator can be used to retrieve golden files from
a sibling flutter/goldens repository.
https://github.com/flutter/flutter/issues/16859
This enables support for a `flutter_test_config.dart` configuration file,
which will be discovered and handed the responsibility of running the
test file (thus allowing it to run pre-test setup on a project level).
https://github.com/flutter/flutter/issues/16859
* Add a `matchesGoldenFile()` async matcher that will match
a finder's widget's rasterized image against a golden file.
* Add support for pluggable image comparison backends
* Add a default backend that does simplistic PNG byte
comparison on locally stored golden files.
* Add support for `flutter test --update-goldens`, which will
treat the rasterized image bytes produced during the test
as the new golden bytes and update the golden file accordingly
Still TODO:
* Add support for the `flutter_test_config.dart` test config hook
* Utilize `flutter_test_config.dart` in `packages/flutter/test`
to install a backend that retrieves golden files from a dedicated
`flutter/goldens` repo
https://github.com/flutter/flutter/issues/16859
