This helps browsers implementing Media Source Extensions (MSE) to
know the exact duration of a Cluster without relying on the next
Cluster.
Change-Id: Idd0422e432430c5702a4864740f89fc6d3c85189
Moving AddAudioTrack into a separate function and keeping it
simple so that it can be re-used from other tests that might
require adding an audio track.
Change-Id: Ia60ed63ddbe617764596eb9c5a2bf96108c47cdd
Some of the muxer tests have been failing because of incorrect
gold files. Updating the gold files and tweaking the tests so that
they pass in a sensible way.
Change-Id: I7d3dda6cacecda526880d6e7623f9a7678b71265
