[telemetry] Change blink_perf back to a full-fledged measurement.

The bisect bots run blink_perf with an individual page to reduce cycle time. Because it can take a page set argument (sort of), it's a measurement (sort of).

BUG=None.
TEST=xvfb-run tools/perf/run_benchmark blink_perf; xvfb-run tools/perf/run_measurement blink_perf third_party/WebKit/PerformanceTests/
TBR=tonyg

Review URL: https://codereview.chromium.org/55583002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232262 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232262