Introduce ADTSStreamParser. Factorize MP3StreamParser and tests.

Factorizes MP3StreamParser into MPEGAudioStreamParserBase for reuse
with a new ADTSStreamParser.  In the process, also factorizes the
MP3StreamParserTest into a new test helper StreamParserTest for
reuse with the ADTSStreamParserTest.

Introduces an adts_constants.{cc,h} to remove duplicate constants
across the AAC and ES ADTS parsers.  Fixes a channel layout bug in
the AAC parser.

sfx.adts test file will be landed manually in a separate change.

BUG=341648,340426
TEST=new unittests pass!

Review URL: https://codereview.chromium.org/120503006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250730 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250730