We don't have profile name available when running with default profile.
With this patch Firefox looks for existing DBus interfaces and tries to pick one
instead of creating a new instance.
MozReview-Commit-ID: 223rRcEvTWv
DBus strings can contain only [a-z][A-Z][0-9]_ chars. Encode profile name (used as part of interface name) by base64 and adjust it to avoid crashes (Bug 1418985).
MozReview-Commit-ID: J2SQHYRcWDW
