MSE: Remove unused |success| StreamParser::InitCB argument
The only current source of a false |success| argument to
StreamParser::InitCB is MPEGAudioStreamParserBase::ParseFrame(), which
should not even run InitCB in that case. This CL removes this redundant
InitCB parameter, preparing for some further refactoring of InitCB and
NewConfigCB for compliant initialization segment received algorithm
implementation.
BUG=249428
TEST=No media_unittest or MSE layout test regressions locally on Linux
Review URL: https://codereview.chromium.org/
935763002
Cr-Commit-Position: refs/heads/master@{#316744}