MSE: Replace crossfade splicing overlap trimming.
Crossfading is quite complex and error prone (source of many
crashes). It is also not necessary for the gapless playback
scenario (handled entirely by partial append window trimming).
The simpler approach is to just trim the existing buffer,
eliminating the overlap.
See MSE spec proposal here:
https://github.com/w3c/media-source/issues/165
BUG=588351, 577438
TEST=new unit tests
Review-Url: https://codereview.chromium.org/2343543002
Cr-Commit-Position: refs/heads/master@{#429394}
11 files changed
