Improve validation when creating audio streams.

BUG=166795
Review URL: https://codereview.chromium.org/11647012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@173981 0039d316-1c4b-4281-b951-d872f2087c98
void AudioInputRendererHost::DoSendRecordingMessage(
    media::AudioInputController* controller) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
}

void AudioInputRendererHost::DoSendRecordingMessage(
    media::AudioInputController* controller) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
}
