SyncPointQueue manages all cue points and returns aligned cue
points to the callers (CueAlignmentHandlers).
CueAlignmentHandler is responsible for aligning cues from different
streams. It uses SyncPointQueue internally to align / synchronize the
cue points.
Issue: #355
Change-Id: I281fecb46a3ca7172d71e7495bdd07b8efdeb283