From
http://blogs.windows.com/msedgedev/2015/05/11/microsoft-edge-building-a-safer-browser/
:
MemGC
As these mitigations have rolled out, attackers have adapted,
inventing new forms of attack. Microsoft in turn has responded
with new memory safety defenses that mitigate the most common
new forms of attack, including and especially use-after-free
vulnerabilities.
MemGC (Memory Garbage Collector) is a memory garbage collection
system that seeks to defend the browser from UAF
(Use-after-free) vulnerabilities by taking responsibility for
freeing memory away from the programmer and instead automating
it, only freeing memory when the automation has detected that
there are no more references left pointing to a given block of
memory.
It sounds like they are using a conservative GC to avoid problems
caused by dangling pointers.
