Migrate webtry to metrics2
Migrate webtry to metrics2

BUG=skia:4899

Review URL: https://codereview.chromium.org/1725123003

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot