Added unittest to WebRtcAudioRenderer. This is to protect the use cases that WebRtcAudioRenderer will be shared by multiple audio tags.

NOTRY=true

BUG=351895,264611,351270

Review URL: https://codereview.chromium.org/199063002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@257388 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed