Dart DevTools CPU Flame Chart shows wrong times

[jensjoha]

Say I do this:

pkg/vm/tool/precompiler2 pkg/_fe_analyzer_shared/test/scanner_benchmark.dart test.aot
out/ReleaseX64/dartaotruntime --enable-vm-service --pause_isolates_on_exit --profiler test.aot pkg/_fe_analyzer_shared/lib/src/parser/parser_impl.dart --bytes

(I have to do the aot compile or the loading of the cpu profile doesn't work: #60041)

and launch devtools. I go to the "CPU Profiler" tab, click "Load all CPU samples" and click "CPU Flame Chart".
The top shows time. Notice how it's already wrong: The computation took ~3 seconds, but it shows - depending on how fast you got here - something else. In my case ~13 seconds:

Then after a while I click the "Load all CPU samples" again, or reload the page (and redo the navigation) it says... more - in my case ~115 seconds:

and hovering something it claims one of the methods have run for 49.9 seconds:

[dart-github-bot]

Summary: DevTools CPU flame chart displays inaccurate execution times. Repeated profile loads show increasingly inflated durations.

[a-siva]

//cc @derekxu16

[derekxu16]

I'm going to close this in favour of flutter/devtools#8870. I have added a comment on that issue explaining why I think this requires changes to DevTools and not to the VM.