Add a histogram to collect how often path degrading is detected when QUIC handshake timed out

Bug: 790547
Change-Id: I0d672ab1c16ef569ba29e6a9840668feddb0722c
Reviewed-on: https://chromium-review.googlesource.com/1149272
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@{#578065}
3 files changed