Stop ResourceCallback from being an on-heap class

third_party/WebKit/Source/core/fetch/Resource.cpp

Index: third_party/WebKit/Source/core/fetch/Resource.cpp
diff --git a/third_party/WebKit/Source/core/fetch/Resource.cpp b/third_party/WebKit/Source/core/fetch/Resource.cpp
index 31065b424de1b0d4ae6081c43870045d0a58e1d1..ca35056b36931d066b15d2287ead0f511db42717 100644
--- a/third_party/WebKit/Source/core/fetch/Resource.cpp
+++ b/third_party/WebKit/Source/core/fetch/Resource.cpp
@@ -226,10 +226,12 @@ void Resource::ServiceWorkerResponseCachedMetadataHandler::sendToPlatform()
     }
 }
 
-class Resource::ResourceCallback final : public GarbageCollectedFinalized<ResourceCallback> {
+// This class cannot be on-heap because the first callbackHandler() call
+// instantiates the singleton object while we can call it in the
+// pre-finalization step.
+class Resource::ResourceCallback final {
 public:
     static ResourceCallback& callbackHandler();
-    DECLARE_TRACE();
     void schedule(Resource*);
     void cancel(Resource*);
     bool isScheduled(Resource*) const;
@@ -238,7 +240,7 @@ private:
 
     void runTask();
     std::unique_ptr<CancellableTaskFactory> m_callbackTaskFactory;
-    HeapHashSet<Member<Resource>> m_resourcesWithPendingClients;
+    HashSet<Persistent<Resource>> m_resourcesWithPendingClients;
 };
 
 Resource::ResourceCallback& Resource::ResourceCallback::callbackHandler()
@@ -249,15 +251,10 @@ Resource::ResourceCallback& Resource::ResourceCallback::callbackHandler()
     //
     // Keep it out of LSan's reach instead.
     LEAK_SANITIZER_DISABLED_SCOPE;
-    DEFINE_STATIC_LOCAL(ResourceCallback, callbackHandler, (new ResourceCallback));
+    DEFINE_STATIC_LOCAL(ResourceCallback, callbackHandler, ());
     return callbackHandler;
 }
 
-DEFINE_TRACE(Resource::ResourceCallback)
-{
-    visitor->trace(m_resourcesWithPendingClients);
-}
-
 Resource::ResourceCallback::ResourceCallback()
     : m_callbackTaskFactory(CancellableTaskFactory::create(this, &ResourceCallback::runTask))
 {