Chromecast: fix accidental dangling reference in CC renderer factory
The last parameter of media::DefaultRendererFactory is audio_config,
which is passed by reference and is assumed to be owned by the caller.
Currently we are passing a reference to local object in there, which
creates dangling reference after we leave local scope. We need to
own and keep AudioHardwareConfig object alive as long as
DefaultRendererFactory is alive.
BUG=none
Review URL: https://codereview.chromium.org/
1167873002
Cr-Commit-Position: refs/heads/master@{#332750}