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
AudioRendererHost::AudioEntry::AudioEntry()
    : stream_id(0),
      pending_close(false) {
}

AudioRendererHost::AudioEntry::AudioEntry()
    : stream_id(0),
      pending_close(false) {
}
