Fixed the valgrind warning in webrtc_audio_capturerer_unittests about using of uninitialized value in media::ToInterleavedInternal.


BUG=324420
TEST=content_unittests --gtest_filter="*WebRtcAudioCapturer*" with valgrind

Review URL: https://codereview.chromium.org/96673002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237933 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237933