Add two histograms for new connection on alternate network.

- Net.QuicStreamFactory.AttemptMigrationBeforeHandshake.FailedConnectionType
tracks the connection type of the default network when the original
connection fails with handshake not confirmed.
- Net.QuicStreamFactory.MigrationBeforeHandshake.NewConnectionType
tracks the connection type of the altenate network when the original
connection fails with handshake not confirmed and a new connection is
about to be retried on the alternate network.

These histograms may give us hints why the altenate network is not
availabe when the connection on the default network fails. Current
theory is that the default network is on Cellular, and there is no
alternate network.

Bug: 790547
Change-Id: Ibfd63efed9a1b72b7d6de95453af55feacd9cef6
Reviewed-on: https://chromium-review.googlesource.com/c/1354320
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Zhongyi Shi <zhongyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612414}