I'm trying to get about:tracing results from a benchmark run. The Perf Dashboard has a convenient |Trace| button so I thought I'd use that:

The tryjob ran successfully, apparently, but there's no trace output. Logs show (stdio attached for posterity):

ChromeTracingStartedError: Tracing is already running on devtools at port localabstract:chrome_devtools_remote on platformbackend <telemetry.internal.platform.android_platform_backend.AndroidPlatformBackend object at 0x7fd86407ce10>.@@@

So run_benchmark.py has a --profile= option. I ran it with --profile=trace locally. Same thing.

So I checked https://www.chromium.org/developers/telemetry/profiling

Ah, "--profile is deprecated". Apparently I should use platform/tracing_controller.py, but the link in the doc is broken. Ok, I can do a search, but there's two versions of it in the source repo and neither seems to be an executable so at this point I'm lost.

Is profiling/tracing still a supported use case? If not, the tools and docs should be more clear about that. run_benchmark --help doesn't mention anything about --profile being deprecated (it does mention that the flag doesn't work with "Timeline Based Measurement" benchmarks but I'm not sure what that means or if its related to my woes).
 

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