No, Oilpan is different; it's a garbage collector for C++ objects, while exact rooting is for JS objects. Oilpan has more in common with the XPCOM cycle collector in purpose (although the approach is different), which Firefox has had for several years now but which WebKit has had no equivalent to.
Doc: https://docs.google.com/document/d/1y7_0ni0E_kxvrah-QtnreMlz...