Previously for the last iframe in a segment, we wait for the next
segment to arrive before writing the EXTINF tag. If an Ad Cue comes
in before the next segment, the EXT-X-PLACEMENT_OPPORTUNITY tag would
be inserted before the iframe in previous segment.
Fixes#378, #396.
Change-Id: I1ede72a4d4edca94781c7b05bc25397d67916d1a
Create an end-to-end test for ad cues. This test's final result is not
correct but illustrates the problem we have in the cue insertion and will
be fixed by a later CL.
Change-Id: Ia8b43a53848941be52cf9ade018668e6477e8df2