Change pruneNoLongerPending to accept Set instead of Collection

Previously while we are looking up the collection using .contains(),
it was an O(n) operation and resulting in degredation of pruning
performance when the number of tasks in storage is high. Change it
to use Set instead.

Change-Id: Ibba32198049536177f51a1c19d79a8ed181faa73
1 file changed
tree: 2fb4065f1e06e41f3f5c78eb1f44e3da143c5f83
  1. .settings/
  2. src/
  3. .gitignore
  4. .mailmap
  5. BUILD
  6. LICENSE