HashMap-based domain lookup in TdsClient

[anikiki]

Task/Issue URL: https://app.asana.com/1/137249556945/project/72649045549333/task/1213796972971719?focus=true

Description

Replaces the per-request linear scan over the full TDS tracker list in TdsClient.matches() with a HashMap-based label-walk lookup, gated by a new optimizeTrackerEvaluationV3 remote feature flag.

For non-tracker URLs (the majority of subresource requests), the linear scan visits every tracker entry before returning false. The new path walks the URL host's labels upward (api.sub.tracker.com → sub.tracker.com → tracker.com) doing a hash lookup at each step, bounded by host label count (typically 2–4 lookups). A local microbenchmark over the real tds.json shows ~90x faster on a mixed URL set; production validation will come from the page-load wide event once V3 is rolled out.

Changes:

• New optimizeTrackerEvaluationV3 toggle on AndroidBrowserConfigFeature (default OFF, internal-always-enabled). The old optimizeTrackerEvaluationV2 toggle is removed.
• V2 (parse host once, linear scan with cached sameOrSubdomain) is now the unconditional fallback when V3 is OFF. The legacy V1 path (re-parsing host per iteration) is removed entirely.
• OptimizeTrackerEvaluationRCWrapper repurposed to source from the V3 toggle; consumer call sites (PageLoadWideEvent, PageLoadedHandler, TrackerDataLoader) are unchanged.
• Telemetry key value renamed tracker_optimization_enabled_v2 → tracker_optimization_enabled_v3 in both PageLoadWideEvent and PageLoadedOfflinePixelSender so the wide-event and offline-pixel pipelines stay in sync. Deliberate metric discontinuity — downstream dashboards keyed on the old name will need updating.
• TdsClientTest re-parametrised across V2/V3 with new V3-specific tests for exact-host match, subdomain match, longest-suffix-wins, no match, null/empty host, single-label host, and non-label-aligned suffix.

Rollback: disable the V3 toggle remotely → users fall back to V2, the path the majority of the user base has been on. The deprecated optimizeTrackerEvaluationV2 remote-config entry is now unreferenced by client code.

Steps to test this PR

V3 enabled (default for internal builds)

• Install the internal build; browse normally — pages load and trackers are blocked.
• Visit a tracker-heavy site (any major news site); confirm the tracker shield count is non-zero and the listed entities match what you'd see on develop.
• Confirm telemetry: the tracker_optimization_enabled_v3 field reads true in the page-load wide event / offline pixel.

V3 disabled (V2 fallback)

• Disable optimizeTrackerEvaluationV3 via remote config; confirm browsing still works and the same tracker entities are blocked on a tracker-heavy site.
• Confirm tracker_optimization_enabled_v3 reads false in telemetry.

Reference test suite

• CI runs RequestBlocklistReferenceTest, SurrogatesReferenceTest, and DomainsReferenceTest — these are the load-bearing behavioural validation against the upstream TDS reference set. They must pass.

NO UI changes

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Note

Medium Risk
Changes core tracker-detection matching behavior and lookup strategy, which could impact blocking decisions or performance if edge cases regress. Also renames telemetry keys, causing metric discontinuity and requiring downstream dashboard updates.

Overview
Adds a new remote-config flag optimizeTrackerEvaluationV3 (internal-by-default) and routes OptimizeTrackerEvaluationRCWrapper to it.

Updates TdsClient to use a HashMap-backed, label-walk domain lookup when V3 is enabled (falling back to the existing subdomain scan when disabled), and wires the flag through TrackerDataLoader.

Renames page-load telemetry from tracker_optimization_enabled_v2 to tracker_optimization_enabled_v3 across wide-event definitions, PageLoadWideEvent, and offline pixel sending, and expands tests (plus an ignored microbenchmark) to validate V3 lookup semantics.

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