This is a follow-up to https://codereview.chromium.org/2382983002/. There is some logic in website_settings.cc to:

1. Show the renegotiation_info extension.
2. Downgrade the security status if we have an SSL 3.0 host (but only on top-level loads).

(1) was probably added back when the renegotiation bug was first found. Trying to enforce it isn't really a priority (it's largely for servers to enforce, not client), so let's just take it out completely.

(2) was originally added when we needed to drop SSL 3.0 for POODLE. It should be a no-op because SSL 3.0 is long gone, but it's reachable if we load an ancient cached SSL 3.0 resource without revalidation. Such resources will also appear in the security panel as SSL 3.0, which is pretty confusing.

SSL 3.0 is long gone, so I propose we drop those cache entries. This will prevent the security panel from showing SSL 3.0 and mean make removing that website_settings.cc check actually a no-op.

https://chromium.googlesource.com/chromium/src/+/master/chrome/browser/ui/website_settings/website_settings.cc#637

Note that dropping those cache entries is not much of a security guarantee because we don't do provenance tracking for complex loads like revalidations or range requests, and doing so is probably unreasonable. See https://groups.google.com/a/chromium.org/d/msg/security-dev/pdvsbRGnKgA/kzhhvnERqGoJ

The motivation is mostly so UI will never show SSL 3.0.