https://bugs.webkit.org/show_bug.cgi?id=123418

Reviewed by Simon Fraser.

Add PlatformCALayer::createCompatibleLayer, which is overridden in
each of the subclasses to create a PlatformCALayer instance of the same
subclass. This is used in TileController to make bare PlatformCALayers
of the correct type (Mac, Win, or Remote).

* platform/graphics/ca/PlatformCALayer.h:
* platform/graphics/ca/mac/PlatformCALayerMac.h:
* platform/graphics/ca/mac/PlatformCALayerMac.mm:
(PlatformCALayerMac::createCompatibleLayer):
* platform/graphics/ca/win/PlatformCALayerWin.cpp:
(PlatformCALayerWin::createCompatibleLayer):
* platform/graphics/ca/win/PlatformCALayerWin.h:
Add createCompatibleLayer and implement it in the subclasses.

* platform/graphics/ca/mac/TileController.mm:
(WebCore::TileController::TileController):
(WebCore::TileController::tiledScrollingIndicatorLayer):
(WebCore::TileController::createTileLayer):
Make use of createCompatibleLayer when creating PlatformCALayers.

* WebProcess/WebPage/mac/PlatformCALayerRemote.cpp:
(PlatformCALayerRemote::createCompatibleLayer):
* WebProcess/WebPage/mac/PlatformCALayerRemote.h:
Add createCompatibleLayer and implement it in the subclasses.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158160 268f45cc-cd09-0410-ab3c-d52691b4dbfc