I've got a patch for this. I'll attach it tomorrow.

https://codereview.chromium.org/2950543002/

Note that *@fb.com is in the AUTHORS for chromium but not v8. Let me know if this requires a different CLA

This is my first v8 patch, please request tests on my behalf.

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/93557496a2315111165b1b6f29ef5b5ba60b1837

commit 93557496a2315111165b1b6f29ef5b5ba60b1837
Author: bgirard <bgirard@fb.com>
Date: Mon Jul 03 22:01:14 2017

Add StartProfiling to filter out v8 warm up

v8.cpu_profiler has a long and variable warm up period. If you look in
tracing that time shows up under V8.Execute which is very misleading. By
adding a tracing category for the time spent in
CpuProfiler::StartProfiling the warm up time can be easily identified or
even filtered out.

With this tracing event the block in StartProfiling correctly described
the time spent prepare v8.cpu_profiler out from V8.Execute

Test by collecting a trace with V8.Execute and look at when a trace
starts generating v8 samples.

BUG= chromium:733853 

Review-Url: https://codereview.chromium.org/2950543002
Cr-Commit-Position: refs/heads/master@{#46393}

[modify] https://crrev.com/93557496a2315111165b1b6f29ef5b5ba60b1837/src/profiler/cpu-profiler.cc

Issue has not been modified or commented on in the last 365 days, please re-open or file a new bug if this is still an issue.

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