find storage history

InspectorHistory* InspectorDOMStorageAgent::findStorageHistory(ErrorString* errorString, const RefPtr<InspectorObject>& storageId, RefPtr<StorageArea>& storageArea, Frame*& targetFrame)
{
    storageArea = findStorageArea(0, storageId, targetFrame);
    if (!storageArea) {
        *errorString = "Storage not found";
        return 0;
    }

    String historyMapKey;
    bool isLocalStorage = false;
    bool success = storageId->getString("securityOrigin", &historyMapKey);
    if (success)
        success = storageId->getBoolean("isLocalStorage", &isLocalStorage);
    if (!success) {
        if (errorString)
            *errorString = "Invalid storageId format";
        return 0;
    }

    historyMapKey.append(isLocalStorage ? "@localStorage" : "@sessionStorage");

    StorageIdToHistoryMap::iterator it = m_storageHistoryMap.find(historyMapKey);
    if (it == m_storageHistoryMap.end())
        it = m_storageHistoryMap.set(historyMapKey, adoptPtr(new InspectorHistory())).iterator;
    ASSERT(it != m_storageHistoryMap.end());
    return it->value.get();
}