Tests for round() method.

Rationale:
While working on some ideas on implementing round(),
I wrote these tests. We might as well use them to
ensure any future work does not break (test also
provides an easy place to add future "difficult" values).

bug=26327751

Change-Id: I911a3e1e5fe45147bc1b7214225c9aec4e979965
3 files changed