SPDY - persist 200 most recently used SPDY settings to perferences file.
This change reduces the size of Preferences file for around 0.5% users
who have lot of entries (some users have more than 10,000 entries).
Per server SpdySettings uses around 74 bytes. This change for some users
could shkrink the preference file by more than 750k bytes).
This change is similar to MRU change for AlternateProtocol.
R=rch@chromium.org
Review URL: https://codereview.chromium.org/
199583005
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257610 0039d316-1c4b-4281-b951-d872f2087c98