Merge "Preload only visible thumbnails and task icons. (Bug 17672056, Bug 18291345)" into lmp-mr1-dev
automerge: 147de3a

* commit '147de3a9766e205af068d1462beaea7a4a9fb9bc':
  Preload only visible thumbnails and task icons. (Bug 17672056, Bug 18291345)