[telemetry] Fix types and type checks of numeric results.

Followup for http://crrev.com/236907

BUG=None.
TEST=None.
TBR=nduca

Review URL: https://codereview.chromium.org/84483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236951 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236951