Use a heap for the released handle list. This will prioritize re-allocating smaller handles. It should not affect performance in most cases, but will prefer allocating handles that are in the "fast" portion of the resource map. BUG=angleproject:1458 Change-Id: Ib2853be936f09fc1e6b5bfb870c360ce8424ab5f Reviewed-on: https://chromium-review.googlesource.com/665993 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>