Chrome_traceSourceOutput trace data to a file in Chrome's trace_event format. This format is compatible with chrome trace viewer chrome://tracing.
Trace viewer is a part of the catapult project (https://github.com/catapult-project/catapult/blob/master/tracing/README.md).
The trace format is documented at: https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview
The object format provided in whole