[wk2] Page Overlays: Don't create backing store until the client asks us to paint
https://bugs.webkit.org/show_bug.cgi?id=112989
<rdar://problem/13355759>

Reviewed by Anders Carlsson.

* WebProcess/WebCoreSupport/WebInspectorClient.cpp:
(WebKit::WebInspectorClient::highlight):
* WebProcess/WebPage/FindController.cpp:
(WebKit::FindController::updateFindUIAfterPageScroll):
Invalidate the entire overlay on installation, to maintain existing behavior
on platforms where the fade-in animation is not performed by invalidating the overlay.

* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::installPageOverlay):
Don't invalidate the overlay upon installation.

* WebProcess/WebPage/mac/TiledCoreAnimationDrawingArea.mm:
(WebKit::TiledCoreAnimationDrawingArea::setPageOverlayNeedsDisplay):
Create backing store for the page overlay layer the first time it is painted into.
(WebKit::TiledCoreAnimationDrawingArea::updateGeometry):
Don't update the size of the page overlay layer unless we intend for it to have backing store.
(WebKit::TiledCoreAnimationDrawingArea::createPageOverlayLayer):
Don't create backing store when we create the page overlay layer.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146551 268f45cc-cd09-0410-ab3c-d52691b4dbfc