Fix a bug in console error metric.
Fix a bug in console error metric.

Events from V8 do not have the source argument anymore.

Bug: chromium:880432
Tbr: d3ffe0e065c2328e497bb32a07f4dcb29138ef5b@chromium.org
Change-Id: I9bf23ef102e0b02f4e5631a58325549492d2f47f
Reviewed-on: https://chromium-review.googlesource.com/1215628
Commit-Queue: Ulan Degenbaev <56dd103d017ceadb708086e2f118997b62b54fda@chromium.org>
Reviewed-by: Ulan Degenbaev <56dd103d017ceadb708086e2f118997b62b54fda@chromium.org>

catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult