Revert "LCP: Use largest painted image for web-exposed entry" [chromium/src : main]
0 views
Skip to first unread message
luci-bisection@appspot.gserviceaccount.com (Gerrit)
Feb 6, 2026, 10:52:36 PM (yesterday) Feb 6
to Scott Haseley, Chromium LUCI CQ, Michal Mocny, AyeAye, Blink W3C Test Autoroller, chromium...@chromium.org
Attention needed from Michal Mocny and Scott Haseley
luci-bi...@appspot.gserviceaccount.com has uploaded the change for review![]( "Open in Gerrit")
luci-bi...@appspot.gserviceaccount.com would like Scott Haseley, Chromium LUCI CQ and Michal Mocny to review this change.
Commit message
Revert "LCP: Use largest painted image for web-exposed entry"
This reverts commit ec442fbb8bd40671c7094470747c870468191800.
Reason for revert:
LUCI Bisection has identified this change as the cause of a test failure. See the analysis: https://ci.chromium.org/ui/p/chromium/bisection/test-analysis/b/5977743482159104
Sample build with failed test: https://ci.chromium.org/b/8690562211477525345
Affected test(s):
[://chrome/test\:browser_tests!gtest::LCPPTimingPredictorBrowserFlagTest#WithKCriticalPathFlag/Flags.0](https://ci.chromium.org/ui/test/chromium/:%2F%2Fchrome%2Ftest%5C:browser_tests%21gtest::LCPPTimingPredictorBrowserFlagTest%23WithKCriticalPathFlag%2FFlags.0?q=VHash%3Aeadb3d206b16d320)
[://chrome/test\:browser_tests!gtest::LCPPTimingPredictorBrowserFlagTest#WithKCriticalPathFlag/Flags.1](https://ci.chromium.org/ui/test/chromium/:%2F%2Fchrome%2Ftest%5C:browser_tests%21gtest::LCPPTimingPredictorBrowserFlagTest%23WithKCriticalPathFlag%2FFlags.1?q=VHash%3Aeadb3d206b16d320)
[://chrome/test\:browser_tests!gtest::LCPPTimingPredictorBrowserTest#Base](https://ci.chromium.org/ui/test/chromium/:%2F%2Fchrome%2Ftest%5C:browser_tests%21gtest::LCPPTimingPredictorBrowserTest%23Base?q=VHash%3Aeadb3d206b16d320)
If this is a false positive, please report it at http://b.corp.google.com/createIssue?component=1199205&description=Analysis%3A+https%3A%2F%2Fci.chromium.org%2Fui%2Fp%2Fchromium%2Fbisection%2Ftest-analysis%2Fb%2F5977743482159104&format=PLAIN&priority=P3&title=Wrongly+blamed+https%3A%2F%2Fchromium-review.googlesource.com%2Fc%2Fchromium%2Fsrc%2F%2B%2F7269039&type=BUG
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 <mmo...@chromium.org>
> Commit-Queue: Scott Haseley <shas...@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1581252}
>
Bug: 454067883
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: Ic5637d16e4206a0bd4fdfc95f47620053649378e
Change diff
Change information
Files:
- M third_party/blink/renderer/core/paint/timing/largest_contentful_paint_calculator.cc
- M third_party/blink/renderer/core/paint/timing/largest_contentful_paint_calculator_test.cc
- M third_party/blink/renderer/platform/runtime_enabled_features.json5
- D third_party/blink/web_tests/external/wpt/largest-contentful-paint/performance-entry-sequence.tentative.html
Change size: M
Delta: 4 files changed, 10 insertions(+), 90 deletions(-)
Related details
Attention is currently required from:
- Michal Mocny
- Scott Haseley
Submit Requirements:
Code-Coverage
Code-Owners
Code-Review
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
luci-bisection@appspot.gserviceaccount.com (Gerrit)
Feb 6, 2026, 10:52:58 PM (yesterday) Feb 6
to Rubber Stamper, Scott Haseley, Chromium LUCI CQ, Michal Mocny, AyeAye, Blink W3C Test Autoroller, chromium...@chromium.org, lighthouse-eng-extern...@google.com, speed-metrics...@chromium.org, jmedle...@chromium.org, blink-...@chromium.org, kinuko...@chromium.org, blink-rev...@chromium.org, blink-revie...@chromium.org
Attention needed from Michal Mocny and Scott Haseley
Message from luci-bi...@appspot.gserviceaccount.com![]( "Open in Gerrit")
LUCI Bisection could not automatically submit this revert because LUCI Bisection has not yet support auto-commit of revert CL for test failure.
Related details
Attention is currently required from:
- Michal Mocny
- Scott Haseley
Submit Requirements:
Code-Coverage
Code-Owners
Code-Review
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Rubber Stamper (Gerrit)
Feb 6, 2026, 10:53:18 PM (yesterday) Feb 6
to luci-bi...@appspot.gserviceaccount.com, Scott Haseley, Chromium LUCI CQ, Michal Mocny, AyeAye, Blink W3C Test Autoroller, chromium...@chromium.org, lighthouse-eng-extern...@google.com, speed-metrics...@chromium.org, jmedle...@chromium.org, blink-...@chromium.org, kinuko...@chromium.org, blink-rev...@chromium.org, blink-revie...@chromium.org
Attention needed from Michal Mocny and Scott Haseley
Rubber Stamper voted Bot-Commit+1![]( "Open in Gerrit")
| Bot-Commit | +1 |
Related details
Attention is currently required from:
- Michal Mocny
- Scott Haseley
Submit Requirements:
Code-Coverage
Code-Owners
Code-Review
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Michal Mocny (Gerrit)
1:19 PM (10 hours ago) 1:19 PM
to luci-bi...@appspot.gserviceaccount.com, Rubber Stamper, Scott Haseley, Chromium LUCI CQ, AyeAye, Blink W3C Test Autoroller, chromium...@chromium.org, lighthouse-eng-extern...@google.com, speed-metrics...@chromium.org, jmedle...@chromium.org, blink-...@chromium.org, kinuko...@chromium.org, blink-rev...@chromium.org, blink-revie...@chromium.org
Attention needed from Scott Haseley
Michal Mocny added 1 comment![]( "Open in Gerrit")
Patchset-level comments
File-level comment, Patchset 1 (Latest):
Michal Mocny . resolved
I'll wait for Scott to decide if Revert is best before branch Monday, but: I see that all three failing tests are for the LCPPTimingPredictor feature, which is still disabled by default, and AFAIK might no longer be planned to ship?
Quickly looking at the tests I can see how the order of expectations might be brittle/need updating, but I haven't had a chance to dig further.
Related details
Attention is currently required from:
- Scott Haseley
Submit Requirements:
Code-Coverage
Code-Owners
Code-Review
Review-Enforcement
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Michal Mocny (Gerrit)
1:20 PM (10 hours ago) 1:20 PM
to luci-bi...@appspot.gserviceaccount.com, Rubber Stamper, Scott Haseley, Chromium LUCI CQ, AyeAye, Blink W3C Test Autoroller, chromium...@chromium.org, lighthouse-eng-extern...@google.com, speed-metrics...@chromium.org, jmedle...@chromium.org, blink-...@chromium.org, kinuko...@chromium.org, blink-rev...@chromium.org, blink-revie...@chromium.org
Attention needed from Scott Haseley
Michal Mocny added 1 comment![]( "Open in Gerrit")
Patchset-level comments
Michal Mocny . resolved
I'll wait for Scott to decide if Revert is best before branch Monday, but: I see that all three failing tests are for the LCPPTimingPredictor feature, which is still disabled by default, and AFAIK might no longer be planned to ship?
Quickly looking at the tests I can see how the order of expectations might be brittle/need updating, but I haven't had a chance to dig further.
Michal Mocny
(In other words, might be worth checking with the feature owners if these tests are needed or could temporarily be disabled-- keeping the tests passing exactly as written might not be desired chrome behaviour)
Reply all
Reply to author
Forward
0 new messages