Schedule trimMemory after drawing the frame

Fixes jank issues where trimMemory gets scheduled during an
animation. trimMemory likely hits code that is not in the
page cache anymore, leading to high execution time because of page
misses. Scheduling it after the next frame has been drawn
minimizes the risk that this page miss actually causes jank.

Test: Boot, switch between a couple of apps.
Bug: 78611607
Change-Id: Ia1fc411fbe6ca07861183ae484124406681118e5