Allows formulas to update on Google Sheets, which uses a Worker to
update them and makes cookie authenticated requests, which was failing
before this commit.
This has the limitation that it has to proxy through the WebContent
process, but that's how the current infrastructure is, which is outside
the scope of this commit.
Instead of wrapping all non-movable members of TransportSocket in OwnPtr
to keep it movable, make TransportSocket itself non-movable and wrap it
in OwnPtr.
