v27.4.0

Added

• JS/CSS coverage collection for Chrome. --chrome.coverage turns it on for 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 — 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. Each entry has a per-file breakdown (url, totalBytes, usedBytes, unusedBytes, unusedPercent) #2480.

Fixed

• HAR post-processing no longer throws when a page has no matching entries. Occasionally a HAR contains a page whose pageref has no entries — typically a navigation that didn't produce any requests, or an extension-injected page. getDocumentRequests and getFinalURL dereferenced shift() / pop() without a guard, and getMainDocumentTimings wrapped its entire per-page loop in a single try/catch so one bad page wiped out the main-document timings for every other page in the same HAR. Downstream this surfaced as a noisy triplet of warnings followed by an empty coach-data payload in sitespeed.io. The three crash points are now guarded and unresolvable pages are skipped #2483.
• Bumped geckodriver to a version with native ARM-64 support #2482.