Use a UniquePtr to clean up global logging std::string*s.
Use a UniquePtr to clean up global logging std::string*s.

This makes valgrind happier.
Bug: 11670287

Change-Id: I957b94cdc177665e66b069e4d2b2b8d0a4b589c8

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst