Provide Observable.timestamp(Scheduler) to be used in the tests.

[vigdorchik]

The test could've used toBlockingObservable, but this hangs, even though timestamped observable is completed.

[cloudbees-pull-request-builder]

RxJava-pull-requests #665 SUCCESS
This pull request looks good

[vigdorchik]

@samuelgruetter @headinthebox please review. I'd also change 2 overloads to the one

Observable.timestamp(s: Option[Scheduler] = None)

but I'm not sure it's ok to break binary compatibility.

[cloudbees-pull-request-builder]

RxJava-pull-requests #671 SUCCESS
This pull request looks good

[samuelgruetter]

LGTM, thanks for contributing!

Regarding

The test could've used toBlockingObservable, but this hangs, even though timestamped observable is completed.

That's not surprising: You can't use toBlockingObservable and TestScheduler in a single threaded test, because you would have to call advanceTimeTo while you're blocking on a method of BlockingObservable.

And regarding

Observable.timestamp(s: Option[Scheduler] = None)

Don't do this, we want to keep it the same way in all operators. But I agree that the way overloads with schedulers are done currently is not good, Scala offers much better ways with implicits. We're still working on this, and will change all operators at once.

[benjchristensen]

From the Scala folks ... should this be updated and merged considered the changes that have happened in the past month?

@headinthebox @samuelgruetter ?

[samuelgruetter]

This can be merged, but once we decide on #815 , it will change again.

[vigdorchik]

I would appreciate a way to have a timestamped stream unit-tested. If this is not with Scheduler parameter, I'm fine.