Add JS/CSS coverage collection for Chrome#2480
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Coverage is exposed two ways. --chrome.coverage runs it on every iteration for users who want the data and accept that detailed V8 coverage deoptimizes scripts and will skew their timing metrics. --enableProfileRun also turns coverage on for Chrome, alongside the existing trace, so users who want coverage without affecting their timings can lean on the same extra-iteration pattern they already use for tracing. When only the profile run produces coverage, the result is merged back into the main browsertime.json so consumers like sitespeed.io see the data in the same place they read every other metric. The per-iteration result includes a per-file breakdown (url, totalBytes, usedBytes, unusedBytes, unusedPercent), so the "which file should I tree-shake" question is answerable from the main JSON alone. Co-authored-by: Claude noreply@anthropic.com Change-Id: I28526039a799d0efa5f1f4da81d6dfa66d1ec8c3
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Coverage is exposed two ways. --chrome.coverage runs it on every
iteration for users who want the data and accept that detailed V8
coverage deoptimizes scripts and will skew their timing metrics.
--enableProfileRun also turns coverage on for Chrome, alongside the
existing trace, so users who want coverage without affecting their
timings can lean on the same extra-iteration pattern they already use
for tracing. When only the profile run produces coverage, the result
is merged back into the main browsertime.json so consumers like
sitespeed.io see the data in the same place they read every other
metric. The per-iteration result includes a per-file breakdown
(url, totalBytes, usedBytes, unusedBytes, unusedPercent), so the
"which file should I tree-shake" question is answerable from the
main JSON alone.
Co-authored-by: Claude noreply@anthropic.com
Change-Id: I28526039a799d0efa5f1f4da81d6dfa66d1ec8c3