Replace SSLProtocolNegotiation histogram with SSLNegotiatedAlpnProtocol.
* Replace sparse histogram recording ALPN/NPN usage and whether there was
overlap or fallback in case of NPN with a new histogram with much fewer
values. This was made possible by NPN being disabled.
* New histogram is recorded with all TLS handshakes, telling us what
percentage of total TLS connections use HTTP/2. (The old histogram was only
recorded when either NPN or ALPN was used, depriving us of this piece of
information.)
* Remove fixed values from enum NextProto; remove commented out historical
values. Note that git cl format puts the new enum on a single line.
BUG=526713
Review-Url: https://codereview.chromium.org/2243453002
Cr-Commit-Position: refs/heads/master@{#418664}
4 files changed
