GitLab

Adds tests for changeType buffering and playback, for every combination
of up to 7 audio-only types, and for every combination of up to 6
video-only types.

Sequence mode is used for these because a buffered range gap and
playback stall occurs across the boundary of any audio-only combination
containing the test MP2TS AAC media in segments mode.

Other CLs include changeType chromium impl (pre-requisite for this CL);
and blink impl and new web-platform tests.

BUG=605134

Change-Id: I34e6afb9ce104497636958ed2892c1bc6134ff73
Reviewed-on: https://chromium-review.googlesource.com/1110521
Commit-Queue: Matthew Wolenetz <wolenetz@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569775}