RSS is the real measurement by which an allocator should be measured
since RSS is the real memory consumed by the process. PSS is a shared
value.
For memory_replay, PSS and RSS should be the same, so this didn't really
matter in practice, but it's better to use the correct name of RSS.
Also, add a small section about fragmentation.
Bug: 138394907
Test: NA
Change-Id: Ic6f982f9c4619f452342e7c105818e33b8b85e44
This includes tests that a native allocator has to pass, and the ways
to benchmark a native allocator on Android.
Test: NA
Change-Id: I5e1f4b3eea46ee2240e63a487ca3dfabecff81c0
