DOM-based SVG resource tracking

third_party/WebKit/Source/core/svg/SVGTreeScopeResources.h

Index: third_party/WebKit/Source/core/svg/SVGTreeScopeResources.h
diff --git a/third_party/WebKit/Source/core/svg/SVGTreeScopeResources.h b/third_party/WebKit/Source/core/svg/SVGTreeScopeResources.h
index 437f5f87a81eae2aef83c8169cc28a4c28b53827..f0025016a639d4be61048c6785cefeef5c424077 100644
--- a/third_party/WebKit/Source/core/svg/SVGTreeScopeResources.h
+++ b/third_party/WebKit/Source/core/svg/SVGTreeScopeResources.h
@@ -5,6 +5,7 @@
 #ifndef SVGTreeScopeResources_h
 #define SVGTreeScopeResources_h
 
+#include "core/dom/IdTargetObserver.h"
 #include "platform/heap/Handle.h"
 #include "platform/wtf/Forward.h"
 #include "platform/wtf/HashMap.h"
@@ -14,8 +15,9 @@
 namespace blink {
 
 class Element;
-class TreeScope;
 class LayoutSVGResourceContainer;
+class SVGElement;
+class TreeScope;
 
 // This class keeps track of SVG resources and pending references to such for a
 // TreeScope. It's per-TreeScope because that matches the lookup scope of an
@@ -28,36 +30,40 @@ class SVGTreeScopeResources
   explicit SVGTreeScopeResources(TreeScope*);
   ~SVGTreeScopeResources();
 
-  void UpdateResource(const AtomicString& id, LayoutSVGResourceContainer*);
-  void UpdateResource(const AtomicString& old_id,
-                      const AtomicString& new_id,
-                      LayoutSVGResourceContainer*);
-  void RemoveResource(const AtomicString& id, LayoutSVGResourceContainer*);
-  LayoutSVGResourceContainer* ResourceById(const AtomicString& id) const;
-
-  // Pending resources are such which are referenced by any object in the SVG
-  // document, but do NOT exist yet. For instance, dynamically built gradients
-  // / patterns / clippers...
-  void AddPendingResource(const AtomicString& id, Element&);
-  bool IsElementPendingResource(Element&, const AtomicString& id) const;
-  void NotifyResourceAvailable(const AtomicString& id);
-  void RemoveElementFromPendingResources(Element&);
+  class Resource : public IdTargetObserver {
+   public:
+    Resource(TreeScope&, const AtomicString& id);
+    ~Resource() override;
 
-  DECLARE_TRACE();
+    Element* Target() const { return target_; }
+    LayoutSVGResourceContainer* ResourceContainer() const;
 
- private:
-  void ClearHasPendingResourcesIfPossible(Element&);
+    void AddWatch(SVGElement&);
+    void RemoveWatch(SVGElement&);
+
+    bool IsEmpty() const;
+
+    DECLARE_TRACE();
 
-  using SVGPendingElements = HeapHashSet<Member<Element>>;
-  using ResourceMap = HashMap<AtomicString, LayoutSVGResourceContainer*>;
+    void NotifyResourceClients();
 
-  void RegisterResource(const AtomicString& id, LayoutSVGResourceContainer*);
-  void UnregisterResource(ResourceMap::iterator);
-  void NotifyPendingClients(const AtomicString& id);
+   private:
+    void IdTargetChanged() override;
 
-  ResourceMap resources_;
-  // Resources that are pending.
-  HeapHashMap<AtomicString, Member<SVGPendingElements>> pending_resources_;
+    Member<TreeScope> tree_scope_;
+    Member<Element> target_;
+    HeapHashSet<Member<SVGElement>> pending_clients_;
+  };
+  Resource* ResourceForId(const AtomicString& id);
+  Resource* ExistingResourceForId(const AtomicString& id) const;
+
+  void RemoveUnreferencedResources();
+  void RemoveWatchesForElement(SVGElement&);
+
+  DECLARE_TRACE();
+
+ private:
+  HeapHashMap<AtomicString, Member<Resource>> resources_;
   Member<TreeScope> tree_scope_;
 };