CryptString is intended for secret data, such as passwords, and the
memory is cleared on deallocation. However, where it is used in
libjingle_xmpp, the password is copied to other objects without any
magic clearing, so the security benefit is questionable.
In addition, CryptString is yet another string class, it's unused
within webrtc, and essentially unmaintained. If we can replace its use
in Chrome, it will be deleted.