Possible regressions with CPU profiler

[kenzieschmoll]

The following items need investigation

• slow performance when processing and filtering a profile - need to profile this code to investigate
• cpu profile caching seems to be broken. For example, selecting a profile that you've already loaded in the performance page should load immediately instead of processing the samples again
• loading a sub profile may be broken (though this could just be a side effect of the above issue). For example, selecting a timeline event that is a child of an event we have already loaded the profile for should generate a sub profile instead of fetching samples.

[srawlins]

The items tracked in this investigation issue have been completed: CPU profiler filtering performance was addressed, profile caching is in place, and sub-profile generation is implemented in CpuProfileDataCache with test coverage in cpu_profile_model_test.dart. Closing this tracking issue as resolved.

If there is more work to do here, please let us know by filing a new issue with up to date information. Thanks!