Add support for symbolization of native heap dumps on official builds.
Add support for symbolization of native heap dumps on official builds.

symbolize_trace will now download symbols from gcs if needed.

BUG=chromium:729151

Review-Url: https://codereview.chromium.org/2902043006

benschmaus/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult-csm,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,benschmaus/catapult,benschmaus/catapult