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As part of the work to simplify the handling of audio data, adding this
class to create a queue of audio data. Using this class will come in a
subsequent CL.

BUG=248989

Review URL: https://chromiumcodereview.appspot.com/17112016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@207761 0039d316-1c4b-4281-b951-d872f2087c98