URL duplication in mouse cursor tests mean minor typos can cause flakiness
https://bugs.webkit.org/show_bug.cgi?id=104952

Patch by Rick Byers <rbyers@chromium.org> on 2013-01-04
Reviewed by Eric Seidel.

Replace the explicit list of images to preload with code that extracts
URLs from style definitions.  Also move all this image preload code to
a common helper file so that it can easily be used by other tests.

* fast/events/mouse-cursor-image-set.html:
* fast/events/mouse-cursor-multiframecur.html:
* fast/events/mouse-cursor.html:
* fast/js/resources/image-preload-helper.js: Added.
(preloadImagesFromStyle):
(onComplete):
(imagesToLoad):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@138857 268f45cc-cd09-0410-ab3c-d52691b4dbfc