The maximum resident memory on the perf test Animation/Balls.html grew from 119MB to 141MB after r215088 <https://trac.webkit.org/r215088>
At the same time, the JSHeap memory shrinked from 1.12MB to 0Bytes.
Probably due to the change in priority of the JSRunLoopTimer. It was G_PRIORITY_DEFAULT before (0), now it's been raised to 200, which is the highest value in the RunLooopSourcePriority enum.
Just to clarify, highest value which means lowest priority. The idea of that change was to give lower priorities to sources used to releases resource, like garbage collector. The memory pressure has the highest priority because in that case releasing resources is urgent. So, I'm not sure this is a problem.