The spec for the Trace Event Format technically requires that all entries have "ts" values, and they do in the profiles recorded using chrome://tracing. We don't actually use those values in the case of "M" (metadata) events, however, and they're semantically meaningless as far as I can tell, so let's stop requiring them.
This allows the files that @aras-p provided in #77 to import successfully.
Fixes#77
This PR implements basic import of profiles from the "Trace Event Format", which is used by `chrome://tracing`, but also which many other tools target as a convenient event tracing format. The spec can be found here: https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview#heading=h.xqopa5m0e28f.
The standard supports a broad set of events, some of which don't yet have any practical way to visualize them in speedscope. This PR implements support for the `B`, `E`, and `X` events, as well as gathering process and thread names via some of the `M` events.
This work was motivated by a generous donation to /dev/color by @aras-p: https://github.com/jlfwong/speedscope/issues/77#issuecomment-455077014Fixes#77
Jamie Wong