Improve DEFINE_STATIC_LOCAL()'s handling of Blink GCed objects.

third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceContainer.cpp

Index: third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceContainer.cpp
diff --git a/third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceContainer.cpp b/third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceContainer.cpp
index 176e2f4b8490e179c86b3f80066578b3230ad0d2..2a692635f40c5040e5fa5bf53617732c2b149248 100644
--- a/third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceContainer.cpp
+++ b/third_party/WebKit/Source/core/layout/svg/LayoutSVGResourceContainer.cpp
@@ -289,17 +289,17 @@ static inline void removeFromCacheAndInvalidateDependencies(LayoutObject* object
     // reference graph adjustments on changes, so we need to break possible cycles here.
     // This strong reference is safe, as it is guaranteed that this set will be emptied
     // at the end of recursion.
-    DEFINE_STATIC_LOCAL(Persistent<SVGElementSet>, invalidatingDependencies, (new SVGElementSet));
+    DEFINE_STATIC_LOCAL(SVGElementSet, invalidatingDependencies, (new SVGElementSet));
 
     for (SVGElement* element : *dependencies) {
         if (LayoutObject* layoutObject = element->layoutObject()) {
-            if (UNLIKELY(!invalidatingDependencies->add(element).isNewEntry)) {
+            if (UNLIKELY(!invalidatingDependencies.add(element).isNewEntry)) {
                 // Reference cycle: we are in process of invalidating this dependant.
                 continue;
             }
 
             LayoutSVGResourceContainer::markForLayoutAndParentResourceInvalidation(layoutObject, needsLayout);
-            invalidatingDependencies->remove(element);
+            invalidatingDependencies.remove(element);
         }
     }
 }