Expose TracingConfig.chrome_trace_config
Expose TracingConfig.chrome_trace_config

This CL exposes chrome_trace_config in TracingConfig, so
we can remove the API indirection in TracingConfig later.

BUG=catapult:#2413

Review-Url: https://codereview.chromium.org/2073443004

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