97ba30eedf
Broke out CNG from AudioDecoder as they didn't really share an interface. Converted the CNG code to C++, to make initialization and resource handling easier. This includes several changes to the behavior, favoring RTC_CHECKs over returning error codes. Review URL: https://codereview.webrtc.org/1868143002 Cr-Commit-Position: refs/heads/master@{#12491}