QUIC - Persist 1000 MRU alternate protocols to preferences file.
+ Flip a coin and if we have persisted 1000 MRU servers, then load only
either 200 or 1000 servers from disk.
+ Persist only one server (or don't duplicate server names) that
spoke QUIC for canonical suffixes like:
+ .c.youtube.com
+ .googlevideo.com
+ Bumped up the version number of http_server_properties.
+ Added two histograms to measure the impact of persisting 1000
alternate protocol servers.
++ Net.AlternateProtocolUsage.200Truncated
++ Net.AlternateProtocolUsage.1000Truncated
R=jar@chromium.org, rch@chromium.org
Review URL: https://codereview.chromium.org/
298683010
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272836 0039d316-1c4b-4281-b951-d872f2087c98