commit f6fbd565237a74628a99e3efd27f821f0081785e
author kenoss <kenoss@chromium.org> Wed Sep 04 00:40:28 2024
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Wed Sep 04 00:40:28 2024
tree 772900e72266c4c2443a4f96c685ebd7f573502d
parent 47d178c2fbb3f5af4a47f8cc3eff956b32dc1c26

Prefetch: Rewrite "wait matching prefetch" loop (Part 5)

This CL introduces a feature flag `kPrefetchNewWaitLoop` and replaces
`PrefetchService::GetPrefetchToServe()` by
`PrefetchMatchResolver2::FindPrefetch()`.

doc: https://docs.google.com/document/d/1i9gXNKiq2l-BEVbBU9UuY6R03KnKsKRLAmJgXD2ZPyk

Intended side effects:

- Replaces UMA
  `PrefetchProxy.AfterClick.BlockUntilHeadDuration.{WasServed}. {SpeculationEagerness}`
  with
  `PrefetchProxy.AfterClick.BlockUntilHeadDuration2.{WasServed}.{SpeculationEagerness}`.
  Before this CL, it is recorded duration from BlockUntilHead for prior
  navigation (e.g. prerender). The latter records blocked duration as
  intended.
- Replaces UMA
  `PrefetchProxy.AfterClick.WasBlockedUntilHeadWhenServing.{SpeculationEagerness}`
  with
  `PrefetchProxy.AfterClick.PrefetchMatchingBlockedNavigationWithPrefetch.{SpeculationEagerness}`.
  The differences for edge cases are unknown. This is mainly for safe
  replacement.

Other behaviors are preserved as much as possible.

Note that the UMA `PrefetchProxy.AfterClick.RedirectChainSize` is
unchanged as the condition of the callsite
`PrefetchContainer::OnReturnPrefetchToServe(true)` is same to the one of `PrefetchContainer::NotifyServeResult(/*is_served=*/true)`.

Note that `PreloadingAttempt.AccurateTriggering` is unchanged while
it's changed on unit tests. Because it works as the following:

1. Changed case in unit tests is that prefetch received non-redirect
   header and is `kServable` state.
2. In this case and with old path,
   `PreloadingDataImpl::DidStartNavigation()` calls
   `PreloadingAttemptImpl::SetIsAccurateTriggering()`. At this timing,
   `PrefetchService::MatchUrl()` can return the correct value as we
   assumed 1.
3. So, the behavior is unchanged.

This CL disables some tests for BlockUntilHead as they depends on the
old code path. We will add similar tests for new path in the next CL.

Fixed: 353489607
Bug: 343867153
Change-Id: Id32a9fdf161e97f7e608945a62a882f48b080a68
Unresolved-Comment-Reason: Leave discussion about metrics to refer in the future. It's OK now.
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5670092
Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Commit-Queue: Ken Okada <kenoss@chromium.org>
Auto-Submit: Ken Okada <kenoss@chromium.org>
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1350517}