Added three histograms to track the following TCP connection latency
intervals.

a) t <= 10ms
b) 10ms < t <= 20ms
c) 20ms < t (or no previous time)

R=jar@chromium.org

Review URL: https://codereview.chromium.org/68793007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235652 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235652
Automated Commit: Committing new LKGM version 4976.0.0 for chromeos.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235653 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235653