Reviewed by Dirk Schulze.

        WebKit shouldn't ignore resource cycles, but break them as Opera does
        https://bugs.webkit.org/show_bug.cgi?id=43031

        Don't ignore resources containing cyclic references, but break them, as discussed on SVG WG mailing lists - to be compatible with Opera which already does that.

        We used to lookup RenderSVGResourceContainers objects, by extracting the URI reference from the SVGRenderStyle, then utilizing getElementById() to lookup the
        node, and access its renderer. Opera ignores such references, if they point to resources that contain cyclic references. Ignoring them would mean we have
        to mutate the render style to empty the resource strings. That obviously doesn't work, as it would break expectations (getComputedStyle, etc.).

        Introduce a SVGResources class that stores pointers to all resources, that can be applied to a RenderObject (clipper/filter/markers/masker).
        Add a SVGResourcesCache class, which is basically a HashMap<RenderObject*, SVGResources*>. Whenever a RenderObject receives style, we extract the URI references
        from the SVGRenderStyle, look up the RenderSVGResourceContainer* objects, and store them in a SVGResources* class. Then we execute a cycle detection logic,
        which detects cyclic references and breaks them. Breaking them means just nulling the pointer to the resource in the SVGResources object. Those SVGResources
        objects are cached, and used throughout the render tree to access resources. This way it's guaranteed that all cyclic references are resolved until layout/paint
        phase begins.

        This is the first chunk, which just adds the new SVGResources/SVGResourcesCache/SVGResourcesCycleSolver files, and does minor cleanups.
        It's not yet glued in and doesn't affect any tests.

        * Android.mk: Add SVGResources.* / SVGResourcesCache.* / SVGResourcesCycleSolver.* to build.
        * CMakeLists.txt: Ditto.
        * WebCore.gypi: Ditto.
        * WebCore.pro: Ditto.
        * WebCore.vcproj/WebCore.vcproj: Ditto. 
        * WebCore.xcodeproj/project.pbxproj: Ditto.
        * rendering/RenderInline.h: Make styleDidChange protected, RenderSVGInline wants to override it.
        * rendering/RenderSVGAllInOne.cpp: Add SVGResources.* / SVGResourcesCache.* / SVGResourcesCycleSolver.* to build.
        * rendering/RenderSVGHiddenContainer.h:
        (WebCore::RenderSVGHiddenContainer::isSVGHiddenContainer): Make isSVGHiddenContainer() private and renderName() public.
        * rendering/RenderSVGResourceContainer.cpp: Added. Moved most methods from the header in the implementation file.
        (WebCore::RenderSVGResourceContainer::RenderSVGResourceContainer):
        (WebCore::RenderSVGResourceContainer::~RenderSVGResourceContainer):
        (WebCore::RenderSVGResourceContainer::idChanged):
        (WebCore::RenderSVGResourceContainer::transformOnNonScalingStroke):
        (WebCore::RenderSVGResourceContainer::containsCyclicReference):
        * rendering/RenderSVGResourceContainer.h: Add stubs, that SVGResourcesCache uses - a follow-up patch will add the logic.
        (WebCore::RenderSVGResourceContainer::addClient):
        (WebCore::RenderSVGResourceContainer::removeClient):
        * rendering/SVGResources.cpp: Added. Holds a list of resources applyable to a RenderObject (fill/stroke, mask/markers/clipper/filter)
        (WebCore::paintingResourceFromSVGPaint): Helper function looking up a RenderSVGResource for a SVGPaint object.
        (WebCore::registerPendingResource): Helper function that register a RenderSVGResource as pending in the SVGDocumentExtensions. 
        (WebCore::SVGResources::buildCachedResources): Build a list of resources for a RenderObject/RenderStyle pair, handles pending resources, if needed.
        (WebCore::SVGResources::invalidateClient): Helper function that calls invalidateClient() on all resources.
        (WebCore::SVGResources::resourceDestroyed): Helper function that calls invalidateClients() on a certain resource, and nulls it.
        (WebCore::SVGResources::buildSetOfResources): Helper function that stashes all resources present in the SVGResources members in a HashSet, used in SVGResourcesCycleSolver.
        (WebCore::SVGResources::resetClipper): Helper methods nulling a resource.
        (WebCore::SVGResources::resetFilter): Ditto.
        (WebCore::SVGResources::resetMarkerStart): Ditto.
        (WebCore::SVGResources::resetMarkerMid): Ditto.
        (WebCore::SVGResources::resetMarkerEnd): Ditto.
        (WebCore::SVGResources::resetMasker): Ditto.
        (WebCore::SVGResources::resetFill): Ditto.
        (WebCore::SVGResources::resetStroke): Ditto.
        (WebCore::SVGResources::dump):
        * rendering/SVGResources.h: Added.
        (WebCore::SVGResources::clipper): Accesor of the cached m_foo variable.
        (WebCore::SVGResources::filter): Ditto.
        (WebCore::SVGResources::markerStart): Ditto.
        (WebCore::SVGResources::markerMid): Ditto.
        (WebCore::SVGResources::markerEnd): Ditto.
        (WebCore::SVGResources::masker): Ditto.
        (WebCore::SVGResources::fill): Ditto.
        (WebCore::SVGResources::stroke): Ditto.
        * rendering/SVGResourcesCache.cpp: Added. Holds a HashMap<RenderObject*, SVGResources*> and utility functions that update/invalidate the cache.
        (WebCore::SVGResourcesCache::SVGResourcesCache):
        (WebCore::SVGResourcesCache::~SVGResourcesCache):
        (WebCore::SVGResourcesCache::addResourcesFromRenderObject): Build a SVGResources object for a RenderObject and adds it to the cache, then detects & breaks cycles using SVGResourcesCycleSolver.
        (WebCore::SVGResourcesCache::removeResourcesFromRenderObject): Remove a SVGResources object from the cache.
        (WebCore::resourcesCacheFromRenderObject): Helper function, retrieving a SVGResourcesCache method from a RenderObject.
        (WebCore::SVGResourcesCache::cachedResourcesForRenderObject): Returns a SVGResources object from the cache.
        (WebCore::SVGResourcesCache::clientLayoutChanged): (static) Calls invalidateClient() on all resources that are used by the passed RenderObject.
        (WebCore::SVGResourcesCache::clientStyleChanged): (static) Updates the cache (calling removeResourceFromRenderObject/addResourcesFrom...) and invalidates resources in the ancestor chain.
        (WebCore::SVGResourcesCache::clientUpdatedFromElement): (static) Does the same, without invalidating the ancestor chain.
        (WebCore::SVGResourcesCache::clientDestroyed): (static) Calls removeResourcesFromRenderObject() on the SVGResourcesCache, for the given renderer.
        (WebCore::SVGResourcesCache::resourceDestroyed): (static) Updates all SVGResources objects in the cache, that refer to the given resource.
        * rendering/SVGResourcesCache.h: Added.
        * rendering/SVGResourcesCycleSolver.cpp: Added. Detects and breaks cyclic references, just the way Opera handles it. Break cycles as they are detected.
        (WebCore::SVGResourcesCycleSolver::SVGResourcesCycleSolver):
        (WebCore::SVGResourcesCycleSolver::~SVGResourcesCycleSolver):
        (WebCore::SVGResourcesCycleSolver::resourceContainsCycles): Operates only on the render tree
        (WebCore::targetReferenceFromResource): Helper method for chainableResourceContainsCycles().
        (WebCore::setFollowLinkForChainableResource): Ditto.
        (WebCore::SVGResourcesCycleSolver::chainableResourceContainsCycles): Handles cycles for resources that are chainable through xlink:href (filter/gradient/pattern).
        (WebCore::SVGResourcesCycleSolver::resolveCycles): Main method executing the cycle breaking logic, utilizing (chainableResource)resourceContainsCycles.
        (WebCore::SVGResourcesCycleSolver::breakCycle): Nulls a resource in the given SVGResources* object, to avoid using an invalid resource while rendering/layouting.
        * rendering/SVGResourcesCycleSolver.h: Added.
        * svg/SVGDocumentExtensions.cpp:
        (WebCore::SVGDocumentExtensions::SVGDocumentExtensions): Create SVGResourcesCache object once per SVGDocumentExtensions.
        * svg/SVGDocumentExtensions.h:
        (WebCore::SVGDocumentExtensions::resourcesCache): Expose accesor method for the SVGResourcesCache.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@64196 268f45cc-cd09-0410-ab3c-d52691b4dbfc