Detect AIR vs Flash in SDK

[Justin Mclean]

Hi,

In fixing FLEX-33728 adding support for imageDecodingPolicy which only exist on 
AIR, I did this:

                        if (imageDecodingPolicy in loaderContext)
                                loaderContext.imageDecodingPolicy = 
imageDecodingPolicy;

Is there a better way to detect if the SDK is being used in AIR?

Thanks,
Justin