Add a new mechanism for watching SVGElement 'href' targets

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

Index: third_party/WebKit/Source/core/svg/SVGURIReference.h
diff --git a/third_party/WebKit/Source/core/svg/SVGURIReference.h b/third_party/WebKit/Source/core/svg/SVGURIReference.h
index e90c7818587376b09d5c25f87d730ef16a9594fa..83887b19f24da6065d69b687139e694e84b0a20f 100644
--- a/third_party/WebKit/Source/core/svg/SVGURIReference.h
+++ b/third_party/WebKit/Source/core/svg/SVGURIReference.h
@@ -21,14 +21,17 @@
 #ifndef SVGURIReference_h
 #define SVGURIReference_h
 
+#include <memory>
 #include "core/CoreExport.h"
 #include "core/dom/Document.h"
 #include "core/svg/SVGAnimatedHref.h"
 #include "platform/heap/Handle.h"
+#include "wtf/Functional.h"
 
 namespace blink {
 
 class Element;
+class IdTargetObserver;
 
 class CORE_EXPORT SVGURIReference : public GarbageCollectedMixin {
  public:
@@ -53,6 +56,14 @@ class CORE_EXPORT SVGURIReference : public GarbageCollectedMixin {
 
   const String& hrefString() const { return m_href->currentValue()->value(); }
 
+  // Create an 'id' observer for the href associated with this SVGURIReference
+  // and its corresponding SVGElement (which should be passed as
+  // |contextElement|.) Will call buildPendingResource() on |contextElement|
+  // when changes to the 'id' are noticed.
+  Element* observeTarget(Member<IdTargetObserver>&, SVGElement&);
+  // Unregister and destroy the observer.
+  static void unobserveTarget(Member<IdTargetObserver>&);
+
   // JS API
   SVGAnimatedHref* href() const { return m_href.get(); }