Verifiable conversions used a NaCl Curve25519 envelope to let
advertisers cryptographically verify a conversion ID extracted
from page HTML or URL redirects and the feature is no longer
needed. This removes verifiable conversion and resource support,
drops the verifiable_advertiser_public_key column via a v55
database migration, removes the conversion envelope from the
confirmation payload, removes ConversionTypeToString now that only
one conversion type remains, switches conversion detection from
OnHtmlContentDidChange to OnTabDidChange, and removes the entire
NotifyTabHtmlContentDidChange IPC pipeline including the mojom
method, AdsClientNotifier, TabManager, and AdsServiceImpl plumbing
that existed solely to deliver page HTML to the conversion engine.
Terry Mancey
c5cff2d121