TextMetrics+FullTextLine.Dispose() gets slower over time until a GC

[seanhalliday]

I have working on some optimizations to some of our controls to make scrolling faster and I noticed that while scrolling it initially was fast but the more I used it, the more laggy it became. When I profiled with dotTrace it showed that FullTextLine.Dispose() was taking more time. If I force a GC.Collect I get speed back and FullTextLine.Dispose is fast again. Unfortunately this calls into PresentationNative.LoDisposeLine which is not open source so I am unable to determine why it gets slower.
Is there a workaround or a method I can call (even via reflection) that would trigger whatever GC.Collect is triggering?