AbstractSimplificationService.ReduceAsync calls Task.WaitAll

[AArnott]

Async methods should not unnecessarily block threads (UI thread or otherwise). This method delegates to a synchronous Reduce method which calls Task.WaitAll.

It appears Task.WaitAll takes a CancellationToken whereas Task.WhenAll does not offer that option. I see Roslyn is passing in a CancellationToken so that may be why WaitAll was chosen. However there are better ways to combine cancellation and async code.

I'll prepare a pull request for this fix.

Ported from https://roslyn.codeplex.com/workitem/471

[heejaechang]

Andrew already sent PR for this.

[srivatsn]

Yes, assigning to you to review and merge that PR (since you've already starting looking at the PR).