This change renames OriginAttributes.mInBrowser to mInIsolatedMozBrowser and
nsIPrincipal::GetIsInBrowserElement to GetIsInIsolatedMozBrowserElement.  Other
methods that pass these values around also have name changes.

Tokens such as "inBrowser" have previously been serialized into cache keys, used
as DB column names, stored in app registries, etc.  No changes are made to any
serialization formats.  Only runtime method and variable names are updated.

No behavior changes are made in this patch, so some renamed methods may have
nonsensical implementations.  These are corrected in subsequent patches
focused on behavior.

MozReview-Commit-ID: 66HfMlsXFLs