[CSS Shaders] Cached validated programs are destroyed and recreated when there is only one custom filter animating
https://bugs.webkit.org/show_bug.cgi?id=96563

Patch by Max Vujovic <mvujovic@adobe.com> on 2012-09-12
Reviewed by Dean Jackson.

Before this patch, in FilterEffectRenderer::build, we would first clear the old effects and
then create the new effects.

Suppose we have one FECustomFilter animating on the page. This FECustomFilter holds the last
reference to the cached validated program. Before this patch, we would first destroy the old
FECustomFilter, which would destroy its cached validated program. Then, we would create the
new FECustomFilter and have to recreate the validated program.

This patch makes FilterEffectRenderer::build keep the old effects around until we're
done creating the new effects. This way, we won't recreate validated programs.

No new tests. We can't test this because the validated program cache is not exposed to web
pages.

* rendering/FilterEffectRenderer.cpp:
(WebCore::FilterEffectRenderer::build):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@128387 268f45cc-cd09-0410-ab3c-d52691b4dbfc