Gallery: faster texture upload

TileTexture.Uploader uses a fixed time slot (4ms) to upload tiles.
However, typical GL idle time is much longer than that. To better
utilize it, a third parameter is added to onGLIdle method to indicate
the due time. This can cut ~170ms on certain devices.

CRs-Fixed: 1024519
Change-Id: I8347b87f85815a4deaf10eb10f234a56b047681e