Use SequencedSocketData in spdy_stream_unittest.

It was using DeterministicSocketData, which is much harder to debug,
and prone to working when it really shouldn't.

Also update SequencedSocketData to have a RunUntilPaused method, and
to support pausing in the middle of a write.

BUG=492684

Review URL: https://codereview.chromium.org/1533613005

Cr-Commit-Position: refs/heads/master@{#365906}
11 files changed