This file cannot be loaded into firefox profiler. To my knowledge, it conforms to the Chrome Trace Event format as specified by Google's documentation. Ref: https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/preview

[
{"name": "Initialization", "cat": "", "ph": "X", "pid": 346905, "tid": 346905, "ts": 2343, "dur": 100}
]

The error message is:

Error: Unserializing the profile failed: Error: This does not appear to be a valid Gecko Profile, there is no meta field.

In fact, Firefox profiler cannot even open the file shown in that document as an example:

[ {"name": "Asub", "cat": "PERF", "ph": "B", "pid": 22630, "tid": 22630, "ts": 829},
  {"name": "Asub", "cat": "PERF", "ph": "E", "pid": 22630, "tid": 22630, "ts": 833} ]

The same file can be opened fine by other tools that support Trace Events format.

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