https://bugs.webkit.org/show_bug.cgi?id=94622

Reviewed by Emil A Eklund.

Source/WebCore:

Attempting to better match author expectations when painting tiled background images. When under
the effects of zoom with sub-pixel layout enabled, the drawn size of a rendered element can
differ depending on its location. This change looks at the size of the scaled tiled background
image size, and either ceils or floors that value depending on if tiling that value will
result in us being one pixel or less short of covering the background size. This is a heuristic,
as sub-pixel/zooming isn't specced.

Test: fast/sub-pixel/scaled-background-image.html

* rendering/RenderBoxModelObject.cpp:
(WebCore::applySubPixelHeuristicForTileSize):
(WebCore):
(WebCore::RenderBoxModelObject::calculateFillTileSize):

LayoutTests:

* fast/sub-pixel/scaled-background-image-expected.html: Added.
* fast/sub-pixel/scaled-background-image.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@132731 268f45cc-cd09-0410-ab3c-d52691b4dbfc