Use DirectExecutor for Task.addOnCompleteListener

[alexvanyo]

The current version of Task.addOnCompleteListener that is being used schedules the listener to run on the main thread. Because we are completing a Deferred or canceling or resuming a continuation, the listener can be run on any thread and therefore we don't need to introduce an unnecessary hop to the main thread if the rest of the work is happening on other threads.

Implementation notes:

• MoreExecutors.directExecutor exists, but I implemented it directly since it is an extremely simple implementation and that avoids introducing any dependency.

• Because we no longer touch the main thread in tests, I was able to remove the FakeAndroid file that was faking the Handler and Looper

This fixes #2990

[qwwdfsad]

Good catch.

Though a lot of tests fail with java.lang.NoClassDefFoundError: android/os/Handler as some parts of the stub library still use TaskExecutors.MAIN_THREAD, e.g. TaskCompletionSource(token) constructor, please address that (probably by returning FakeAndroid back)

[alexvanyo]

Ah, yep I can reproduce locally after a clean build, not sure how those passed for me before.

I added FakeAndroid back, and rebased against develop to pull in the changes #2996.

[qwwdfsad]

Thanks!

[pmoons]

Curious when the next release will be cut that includes this change. I have a feeling .await() is currently blocking execution in a test I am trying to write because it is trying to execute on the main thread.

https://stackoverflow.com/questions/69693218/how-to-run-an-integration-test-for-the-repository-layer-of-an-android-app-with-f