Fix vulcanized Trace Viewer syntax error
Fix vulcanized Trace Viewer syntax error

This patch fixes the syntax error caused by using an ES6 class
declaration in non-strict mode (the vulcanized trace), which is not
supported by Chrome yet.

BUG=#1714

Review URL: https://codereview.chromium.org/1410353006

catapult-project/catapult,catapult-project/catapult,SummerLW/Perf-Insight-Report,benschmaus/catapult,benschmaus/catapult,SummerLW/Perf-Insight-Report,benschmaus/catapult,catapult-project/catapult,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,sahiljain/catapult,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,catapult-project/catapult,benschmaus/catapult,SummerLW/Perf-Insight-Report,benschmaus/catapult,benschmaus/catapult,sahiljain/catapult,catapult-project/catapult-csm,sahiljain/catapult,sahiljain/catapult,catapult-project/catapult,sahiljain/catapult,catapult-project/catapult-csm,SummerLW/Perf-Insight-Report,catapult-project/catapult-csm,catapult-project/catapult-csm,benschmaus/catapult,sahiljain/catapult