AES and HmacSHA256 symmetric keys can now be imported into
AndroidKeyStore. These keys cannot yet be used.
Bug: 18088752
Change-Id: Iad2fd49d15ac4c2d676abe1153f5b5f0b6ff496c
Add exposition about the use cases for AndroidKeyStore and links to the
API sample application for different use cases.
Bug: 8608817
Change-Id: Ic4ce9405781c92f12687895b28c671661ea5524f