Cast: Using a min filter to compute time offset

Modifying the time offset filter to take to minimum of the first 10 values. 
Once ten offset values were seen, the value will be constant for the entire session. 
This may be justified by the fact we are seeking the offset between sender and
 receiver without accounting the network jitter.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=255166

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=256134

Review URL: https://codereview.chromium.org/186043003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@256342 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 256342