Replace AudioDecoderConfig with simple accessors on AudioDecoder.

Replace AudioDecoderConfig with simple accessors on AudioDecoder.

AudioDecoderConfig was being used as a struct for outputting format information to an AudioRenderer. This was confusing and in contrast to VideoDecoderConfig, which is is actually used as input to configure a video decoder!

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=101563

[Ami GONE FROM CHROMIUM, 2011-09-11 15:04:11]

explicit ReviewConfig(LGTM);