IndexedDB: Have IDBCursor and IDBRequest explicitly break ref cycles

Source/modules/indexeddb/IDBCursor.h

Index: Source/modules/indexeddb/IDBCursor.h
diff --git a/Source/modules/indexeddb/IDBCursor.h b/Source/modules/indexeddb/IDBCursor.h
index cf26440f5e2b0ce4ec1294ce7fd3e5639c27889d..b56cde76bc059f454163ebb98daaafb442e6d95e 100644
--- a/Source/modules/indexeddb/IDBCursor.h
+++ b/Source/modules/indexeddb/IDBCursor.h
@@ -46,7 +46,7 @@ class IDBRequest;
 class ScriptExecutionContext;
 class SharedBuffer;
 
-class IDBCursor : public ScriptWrappable, public RefCounted<IDBCursor> {
+class IDBCursor : public ScriptWrappable, public WTF::RefCountedBase {
 public:
     static const AtomicString& directionNext();
     static const AtomicString& directionNextUnique();
@@ -80,6 +80,15 @@ public:
     void close();
     void setValueReady(PassRefPtr<IDBKey>, PassRefPtr<IDBKey> primaryKey, PassRefPtr<SharedBuffer> value);
     PassRefPtr<IDBKey> idbPrimaryKey() { return m_primaryKey; }
+    IDBRequest* request() { return m_request.get(); }
+
+    void deref()

[alecflett, 2013/09/06 17:56:35]

can/should be OVERRIDE?

[jsbell, 2013/09/06 18:07:43]

Nope, not here. T::deref() is required by the RefPtr<T> family of templates but
not provided by WTF::RefCountedBase.

It's virtual/OVERRIDE in IDBRequest because it's declared as virtual deref() = 0
in IDBCallbacks since we pass RefPtr<IDBCallbacks> around.

(Sorting that mess out is why I let this approach linger for so long!)

+    {
+        if (derefBase())
+            delete this;
+        else if (hasOneRef())
+            checkForReferenceCycle();
+    }
 
 protected:
     IDBCursor(PassRefPtr<IDBCursorBackendInterface>, IndexedDB::CursorDirection, IDBRequest*, IDBAny* source, IDBTransaction*);
@@ -88,6 +97,7 @@ protected:
 private:
     PassRefPtr<IDBObjectStore> effectiveObjectStore();
 
+    void checkForReferenceCycle();
     bool isDeleted() const;
 
     RefPtr<IDBCursorBackendInterface> m_backend;
@@ -95,7 +105,6 @@ private:
     const IndexedDB::CursorDirection m_direction;
     RefPtr<IDBAny> m_source;
     RefPtr<IDBTransaction> m_transaction;
-    IDBTransaction::OpenCursorNotifier m_transactionNotifier;
     bool m_gotValue;
     bool m_keyDirty;
     bool m_primaryKeyDirty;