Revert "Make CFX_WideString::LockBuffer() completely unused."

This reverts commit ee7412f5aef353e5c6f1a64d0e1708ed926869d9.
Reason for revert: VS compile broke.

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1106333003
4 files changed