Implement CSS3 Images cross-fade() image function

Implement CSS3 Images cross-fade() image function
https://bugs.webkit.org/show_bug.cgi?id=52162
<rdar://problem/10209254>

Patch by Tim Horton <hortont424@gmail.com> on 2011-11-17
Reviewed by Simon Fraser.

Fix fast/css/getComputedStyle/computed-style-cross-fade.html to use the "dummy" protocol for its
images, so that we don't have loading errors.

Unskip the test on Qt.

Remove the (now) unnecessary Gtk baselines.

* fast/css/getComputedStyle/computed-style-cross-fade-expected.txt:
* fast/css/getComputedStyle/computed-style-cross-fade.html:
* platform/gtk/fast/css/getComputedStyle/computed-style-cross-fade-expected.txt: Removed.
* platform/qt/Skipped:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@100687 268f45cc-cd09-0410-ab3c-d52691b4dbfc