Bug 179931 Provide new interface IStyle to let extension return the style properties values
Provide the IStyle interface to let extension user can return the style property value list for their extension elements.
model/org.eclipse.birt.report.model.tests/test/org/eclipse/birt/report/model/extension/PeerExtensionTest.java
* @throws Exception
	 */
	public void testExtensionLoaderErrorHandler( ) throws Exception
	{
		MetaDataDictionary dd = MetaDataDictionary.getInstance( );
		assertTrue( dd.getExtensions( ).size( ) >= 2 );
		assertNull( dd.getExtension( "wrongTestExtension" ) ); 
	}
	protected static final String TESTING_TABLE = "TestingTable"; 
	protected static final String TABLE = "Table";
	/**
	 * Tests extension allowed units.
	 * 
	 * @throws Exception
	 */
	public void testExtensionAllowedUnits( ) throws Exception
	{
		
		MetaDataDictionary dd = MetaDataDictionary.getInstance( );
		ExtensionElementDefn extDefn = (ExtensionElementDefn) dd
				.getExtension( TESTING_TABLE );
		IPropertyDefn defn = extDefn.getProperty( "width" ); 
		IChoiceSet set = defn.getAllowedChoices( );
		assertNotNull( set.findChoice( "in" ) );
		assertNotNull( set.findChoice( "cm" ) );
		assertNull( set.findChoice( "mm" ) );
		assertNull( set.findChoice( "pt" ) );
		set = dd.getElement( TABLE )
				.findProperty( "width" ).getAllowedChoices( ); 
		assertNotNull( set.findChoice( "in" ) );