core(lantern): account for slow document response in LCP - #17150
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hjanuschka wants to merge 1 commit into
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core(lantern): account for slow document response in LCP#17150hjanuschka wants to merge 1 commit into
hjanuschka wants to merge 1 commit into
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Use the main document's response time when it exceeds Lantern's origin-level estimate so simulated LCP includes high backend latency. Fixes: GoogleChrome#16213
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Summary
Lantern estimates server response time using the median across an origin. When the main document is much slower than static resources on the same origin, that median can make simulated LCP occur before the observed TTFB.
Use the main document's estimated response time when it exceeds the response time used by the simulation. Apply the difference to the simulated LCP and its optimistic and pessimistic estimates.
Add regression coverage for a slow main document and update the expected LCP breakdown timings.
Related Issues/PRs
Fixes #16213