[polymer] Use classes intead of attributes for 'hidden' in tab view
[polymer] Use classes intead of attributes for 'hidden' in tab view

BUG=catapult:#2285
NOPRESUBMIT=true
NOTRY=true

Review-Url: https://codereview.chromium.org/1958693002

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