[ Merge of http://go/wvgerrit/119806 ]
This change replaces all calls for base64 encoding which first converts
a string to a vector. The new base64 encoding function allow for
encoding binary data contained within strings.
Bug: 181732604
Test: Android unittests
Change-Id: Ibfe79dba99e6a2ee2f2a96e85b62fbd22519aea7