Implementing these in the extension wouldn't be all that hard. At least for now, though, I doubt we want to do that: as long as we're running in the same process as all other content, this opens a side channel through which other sites can be attacked. That is exactly the reason why JS engines don't expose this information to content. The documentation for `flash.system.System.freeMemory` contains this gem: "Use this property to monitor garbage collection", so these are meant precisely for the use case we want to prevent. (Note that as of now, the Flash player might actually grant a vector for this kind of attack, depending on whether these numbers are accurate with the plugin running in its own process.) We might get away with implementing them once we have moved to an e10s process, but a careful analysis would have to be done first.
This bug does not need to block Shumway's 1.0 milestone for ads.