telemetry: Smoothness measurement cleanup.

removed all metrics except for:
- frame_times (list of raw frame times)
- mean_frame_time (arithmetic mean of frame times; NOT the generalized mean)
- jank (absolute discrepancy of frame time stamps)
- mostly_smooth (were 95 percent of the frames hitting 60 fps; boolean value)

R=nduca@chromium.org, tonyg@chromium.org
BUG=264308

Review URL: https://codereview.chromium.org/25360002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226114 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226114