Reland "LCP: Use largest painted image for web-exposed entry"#57666
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Reland "LCP: Use largest painted image for web-exposed entry"#57666chromium-wpt-export-bot wants to merge 1 commit intomasterfrom
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This is a reland of commit ec442fbb8bd40671c7094470747c870468191800. The reland updates the html for the failing tests to wrap each image in a div to prevent <body> from being an LCP candidate due to aggregated whitespace (crbug.com/466437443), which breaks test assumptions. Original change's description: > LCP: Use largest painted image for web-exposed entry > > We track both a largest painted image and largest pending image for LCP. > The largest painted image corresponds to the largest image we have > presentation time for. The largest pending image is the largest image > we've encountered but don't yet have presentation time for, i.e. because > it's still loading. > > The pending/painted distinction is used to prevent recording metrics for > pages that haven't finished loaded, but it also determines what gets > emitted to performance timeline (we test largest based on pending, not > painted). This causes us to suppress emitting new LCP candidates that > are smaller than the largest pending image, but larger than anything > presented so far, which is not specced behavior. > > This CL changes it so that we emit candidates based on the largest > painted image instead of largest pending image. This does not affect > UKM/metrics. This matches the behavior agreed upon by the WebPerf > Working Group at TPAC '25. > > Note: more changes are required for soft navs to match this behavior > since candidates can be overwritten during rendering/paint. This isn't > a problem for hard LCP since candidates are updated during presentation > callbacks, which are based on frame index. > > Chromestatus: https://chromestatus.com/feature/5167930847395840 > > Bug: 454067883 > Change-Id: I5275906769b07aca6c671c846756070333f2b09c > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7269039 > Reviewed-by: Michal Mocny <mmocny@chromium.org> > Commit-Queue: Scott Haseley <shaseley@chromium.org> > Cr-Commit-Position: refs/heads/main@{#1581252} Bug: 454067883 Change-Id: Ib49860a2578c070a4ecd504b677d4c7ba02c847b Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7558997 Reviewed-by: Michal Mocny <mmocny@chromium.org> Commit-Queue: Scott Haseley <shaseley@chromium.org> Cr-Commit-Position: refs/heads/main@{#1582017}
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This is a reland of commit ec442fbb8bd40671c7094470747c870468191800.
The reland updates the html for the failing tests to wrap each image in
a div to prevent <body> from being an LCP candidate due to aggregated
whitespace (crbug.com/466437443), which breaks test assumptions.
Original change's description:
Bug: 454067883
Change-Id: Ib49860a2578c070a4ecd504b677d4c7ba02c847b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7558997
Reviewed-by: Michal Mocny <mmocny@chromium.org>
Commit-Queue: Scott Haseley <shaseley@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1582017}