Start refactoring Filter code to reuse CachedSVGDocument for clipPath
https://bugs.webkit.org/show_bug.cgi?id=126069

Reviewed by Andreas Kling.

Smaller refactoring of the CSS filter style resolver code. Previously the code
requested the FilterOperations list from RenderStyle and compared the content
in this list with an internal map. Then the resource loading was triggered.
With the refactoring we do not request the list from RenderStyle anymore but
rely on the hash map data entirely.

* css/StyleResolver.cpp:
(WebCore::StyleResolver::loadPendingSVGDocuments):
* platform/graphics/filters/FilterOperation.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@160973 268f45cc-cd09-0410-ab3c-d52691b4dbfc