In certain circumstances, the .packages file or dart cache could be missing - since the tool runs from a snapshot this is otherwise fine. 

b1af234b7 Disable the use of the API_AVAILABLE macro in Skia in iOS release builds. (flutter/engine#17213) (#52924)

* Allow projects that don't have tests on every platform.
  We don't really need to enforce that random projects have
  tests on every platform.

* Add some text at the end of the shard so we know it's
  actually running all the tests.

046a4a6c2 Roll src/third_party/skia 1171d314efc7..4b55ff097b9d (2 commits) (flutter/engine#17214) (#52917)

Reland of #52091

This reverts commit f65421aa.

Remove dependency injection from GenSnapshot and AotBuilder and update tests to use FakeProcessManager

* Do not throw when trying to discover a fuchsia device and the sshConfig is invalid

216c420a2 Roll src/third_party/skia afa83bc20b2c..d3b92b910ce0 (2 commits) (flutter/engine#17201) (#52865)

* Fix web test flakiness; enable web golden tests

The fix is three-part:

- Only allow one test to load _and_ test at any point in time.
- Use a fresh Chrome instance for each test file.
- Increase Cirrus resources.

The first two changes only fix the "Unknown error loading" error, but not hanging tests. The resource increase also prevents hanging tests.

Other minor changes:

- Remove test batching (it's no longer necessary)
- Fix the Chrome class, which was using the wrong Completer.