Avoids crash in WebRTC audio clients for 96kHz render rate on Mac OSX.

      TBR=xians
BUG=166523
TEST=Misc set of WebRTC audio clients on Mac.

Review URL: https://codereview.chromium.org/11773017

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175323 0039d316-1c4b-4281-b951-d872f2087c98