GitLab

Change MigrationBeforeHandshake2 to track explicitly labeled retried
connection. ConnectionOnNonDefaultNetwork will track those connection
that started on the default network but network change is encountered
during connection setup.

Additionally, add two more histograms
- MigrationBeforeHandshakeFailedReason will track the net error code
returned when an error is encountered by the new connection on the
alternate network;
- NetworkChangeDuringMigrationBeforeHandshake will track how often the
default network is changed during migration before handshake.

Bug: 790547
Change-Id: I3ebd0e6a05a1a56d45326917f341095594333564
Reviewed-on: https://chromium-review.googlesource.com/c/1352749Reviewed-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@{#611885}