[CR134] Investigate impact of upstream removal of kReduceCookieIPCs

[emerick]

Description

Now that kReduceCookieIPCs has been fully removed upstream, we should investigate if we need a better approach to handling that in light of ephemeral storage. We previously disabled kReduceCookieIPCs since we can switch the cookie storage backend at runtime and thus can't use reduced IPCs when accessing cookies. We currently have an override in place in chromium_src/third_party/blink/renderer/core/loader/cookie_jar.cc to deal with the loss of this flag, but we should investigate if it can be improved.

cc: @goodov