Bug 971693 - Fallback properly when WASAPI does not give us a stream format suggestion. r=kinetik

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extra : rebase_source : 495fdf5ad7f4a1069d9c0b9db186a0b717d18759
Bug 976471 - Implement AnalyserNode.getFloatTimeDomainData(). r=karlt

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extra : rebase_source : cfe6f31f7991c84cf8e0f2679cd89560260d0f40