Pass through channel layout on OSX if hardware supports it.

Allows OSX to handle remapping channels according to a user's
preferences instead of forcing us to handle it.

BUG=266674
TEST=Multichannel users report proper output.
NOTRY=true

Review URL: https://codereview.chromium.org/132873002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244306 0039d316-1c4b-4281-b951-d872f2087c98
Disable unit tests that fail on cros.

Some of these tests need to be fixed and others should probably stay disabled.

BUG=331940
TEST=manual

Review URL: https://codereview.chromium.org/132923002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244307 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244307