Add stacktrace to deadline exceeded error.

[tarobins]

BUG: https://github.com/grpc/grpc-dart/issues/573

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: tarobins / name: Tom Robinson (58e952077730e73c2816baf2e6fe0e2a78605693)

[tarobins]

If you have suggestions on how to test this change, please let me know.

[mraleph]

@tarobins does attaching this stack trace actually communicate any additional information? It's always going to be the same: a bunch of internal frames related to the timer implementation and the ClientCall._onTimedOut frame at the top.

[tarobins]

@mraleph

Yes, you are correct. I thought I saw something useful when I was testing the change, but perhaps I was just overly optimistic.

On the other hand, I spent a bunch of time trying to figure out why there was no stack trace. Had I seen the, even not particularly useful, one that this change provides, I would have at least understood where the error was appearing in the grpc library code rather than chasing why there was no stack trace. That said, I'm going to see if I can improve the situation more, so no need for you to review this change further right now.

Thanks.

[mraleph]

Closing as stale for now.