Support Chrome trace viewer format

Chrome's [trace viewer](https://github.com/catapult-project/catapult/blob/master/tracing/docs/getting-started.md) has a [trace file format](https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/edit?usp=sharing). @legneato pointed out that buck supports generating that format, and this tool could too. That would mean having access to a much nicer viewing interface!