programatic uploads of profiles

[clarkbw]

Coming from issue https://github.com/devtools-html/perf.html/issues/331#issuecomment-301916292

a file picker would allow programmatic uploads of profiles from https://github.com/jrmuizel/perf-convert

For what you need we should extract a node module out of our profile handling + sharing code that you could reuse.

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