Adjust atlas tracking to get better usage.

Only overwrite LRU plots if they've aged out or we're at max pagecount.
Make sure we only increment flush counts if the atlas has been used.

Bug: skia:3550
Change-Id: I5c41e20f6c7db818dc08629d5f74401552ddf32f
Reviewed-on: https://skia-review.googlesource.com/51243
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed