IndexedDB: Have IDBCursor and IDBRequest explicitly break ref cycles

Source/modules/indexeddb/IDBCursor.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 28 matching lines @@
 
 class DOMRequestState;
 class ExceptionState;
 class IDBAny;
 class IDBCallbacks;
 class IDBCursorBackendInterface;
 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();
     static const AtomicString& directionPrev();
     static const AtomicString& directionPrevUnique();
 
     static IndexedDB::CursorDirection stringToDirection(const String& modeString, ExceptionState&);
     static const AtomicString& directionToString(unsigned short mode);
 
     static PassRefPtr<IDBCursor> create(PassRefPtr<IDBCursorBackendInterface>, IndexedDB::CursorDirection, IDBRequest*, IDBAny* source, IDBTransaction*);
@@ skipping 13 matching lines @@
 
     bool isKeyDirty() const { return m_keyDirty; }
     bool isPrimaryKeyDirty() const { return m_primaryKeyDirty; }
     bool isValueDirty() const { return m_valueDirty; }
 
     void continueFunction(PassRefPtr<IDBKey>, ExceptionState&);
     void postSuccessHandlerCallback();
     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*);
     virtual bool isKeyCursor() const { return true; }
 
 private:
     PassRefPtr<IDBObjectStore> effectiveObjectStore();
 
+    void checkForReferenceCycle();
     bool isDeleted() const;
 
     RefPtr<IDBCursorBackendInterface> m_backend;
     RefPtr<IDBRequest> m_request;
     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;
     bool m_valueDirty;
     RefPtr<IDBKey> m_key;
     RefPtr<IDBKey> m_primaryKey;
     RefPtr<SharedBuffer> m_value;
 };
 
 } // namespace WebCore
 
 #endif // IDBCursor_h