Privacy: Add statement that all values exposed or inferable by the application must be per-origin

[ddorwin]

We have a clear requirement that (most) identifiers are per-origin and that persisted data must be clearable, but I don't believe there is a single place that says most values (Permanent Identifiers being the obvious exception), both persisted and not, must be per-origin and not be accessible or inferable by other origins.

Some references to #per-origin-identifiers (now #per-origin-per-profile-identifiers) may not actually be related to identifiers and should instead point to such a requirement.

I believe there are some references in the MediaKeys and/or MediaKeySessions sections, and the web platform relies on origins, but it is still worth making a clear statement and having a reference target that is not specific to identifiers.

[paulbrucecotton]

@ddorwin and @mwatson2 : What is the status of the two "privacy" V1NonBlocking issues ie ISSUE-237 and ISSUE-242?

[jdsmith3000]

I see your comment about persisted or not, but is this concern not sufficiently addressed by Information Stored on User Devices for V1?

[ddorwin]

PR #328.