Bug 186940 Style name in theme cannot be identify by auto when reopen the library[01]
Description: Style name in theme cannot be identify by auto when reopen the library[01] Step: 1.Open a library and add a theme 2.New a style on the theme and use the default name that is "NewStyle" 3.Save the library, close it and reopen it again. 4.New another style on the same theme Actual result: The default style name on second times is also "NewStyle" Exception result: The default style name on second times is "NewStyle1"
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/api/ElementFactory.java
*            the required extension name
	 * @param parent
	 *            a given parent element.
	 * @return a handle to extended item, return <code>null</code> if the
	 *         definition with the given extension name is not found
	 * @throws ExtendsException
	 */
	private ExtendedItemHandle newExtendedItem( String name,
			String extensionName, ExtendedItemHandle parent )
			throws ExtendsException
	{
		MetaDataDictionary dd = MetaDataDictionary.getInstance( );
		ExtensionElementDefn extDefn = (ExtensionElementDefn) dd
				.getExtension( extensionName );
		if ( extDefn == null )
			return null;
		if ( parent != null )
			assert ( (ExtendedItem) parent.getElement( ) ).getExtDefn( ) == extDefn;
		if ( !( extDefn instanceof PeerExtensionElementDefn ) )
			throw new IllegalOperationException(
					"Only report item extension can be created through this method." ); 
		ExtendedItem element = new ExtendedItem( name );
		
		element.setProperty( IExtendedItemModel.EXTENSION_NAME_PROP,
				extensionName );
		if ( parent != null )
		{
			element.getHandle( module ).setExtends( parent );
		}
		module.makeUniqueName( element );