IndexedDB: Have IDBCursor and IDBRequest explicitly break ref cycles

Source/modules/indexeddb/IDBCursor.cpp

 /*
  * 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 62 matching lines @@
     return prevunique;
 }
 
 
 IDBCursor::IDBCursor(PassRefPtr<IDBCursorBackendInterface> backend, IndexedDB::CursorDirection direction, IDBRequest* request, IDBAny* source, IDBTransaction* transaction)
     : m_backend(backend)
     , m_request(request)
     , m_direction(direction)
     , m_source(source)
     , m_transaction(transaction)
-    , m_transactionNotifier(transaction, this)
     , m_gotValue(false)
     , m_keyDirty(true)
     , m_primaryKeyDirty(true)
     , m_valueDirty(true)
 {
     ASSERT(m_backend);
     ASSERT(m_request);
     ASSERT(m_source->type() == IDBAny::IDBObjectStoreType || m_source->type() == IDBAny::IDBIndexType);
     ASSERT(m_transaction);
     ScriptWrappable::init(this);
@@ skipping 173 matching lines @@
 void IDBCursor::postSuccessHandlerCallback()
 {
     if (m_backend)
         m_backend->postSuccessHandlerCallback();
 }
 
 void IDBCursor::close()
 {
     // The notifier may be the last reference to this cursor.
     RefPtr<IDBCursor> protect(this);
-    m_transactionNotifier.cursorFinished();
-    if (m_request) {
-        m_request->finishCursor();
-        m_request.clear();
-    }
+    m_request.clear();
     m_backend.clear();
 }
 
+void IDBCursor::checkForReferenceCycle()
+{
+    // If this cursor and its request have the only references
+    // to each other, then explicitly break the cycle.
+    if (!m_request || m_request->getResultCursor() != this)
+        return;
+
+    if (!hasOneRef() || !m_request->hasOneRef())
+        return;
+
+    m_request.clear();
+}
+
 ScriptValue IDBCursor::key(ScriptExecutionContext* context)
 {
     m_keyDirty = false;
     DOMRequestState requestState(context);
     return idbKeyToScriptValue(&requestState, m_key);
 }
 
 ScriptValue IDBCursor::primaryKey(ScriptExecutionContext* context)
 {
     m_primaryKeyDirty = false;
@@ skipping 83 matching lines @@
     case IndexedDB::CursorPrevNoDuplicate:
         return IDBCursor::directionPrevUnique();
 
     default:
         ASSERT_NOT_REACHED();
         return IDBCursor::directionNext();
     }
 }
 
 } // namespace WebCore