https://bugs.webkit.org/show_bug.cgi?id=119282

Reviewed by Simon Fraser.

No new tests, just a refactoring.

The bodies of ensureTilesForRect and revalidateTiles are nearly equivalent.

* platform/graphics/ca/mac/TileController.h:
Add an enum, NewTileType, to note whether the tiles created by ensureTilesForRect will
be primary coverage tiles or secondary out-of-view tiles.

* platform/graphics/ca/mac/TileController.mm:
(WebCore::TileController::prepopulateRect):
Move the code to see if we already have the requisite tiles in the
primary coverage rect, as well as our call to updateTileCoverageMap,
out into prepopulateRect, to generalize ensureTilesForRect.

(WebCore::TileController::revalidateTiles):
Make use of ensureTilesForRect. The platformCALayerDidCreateTiles call will happen there, now.

(WebCore::TileController::ensureTilesForRect):
Make ensureTilesForRect return the rect that it created tiles for, and only put
tiles in a cohort if we're creating secondary tiles.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@154413 268f45cc-cd09-0410-ab3c-d52691b4dbfc