Bug 299340 [CommonNavigator] Enable new CNF tests
Enable the contributed CNF tests, make minor test improvements.
tests/org.eclipse.ui.tests.navigator/src/org/eclipse/ui/tests/navigator/M12Tests.java
TreeItem[] p1Children = rootItems[_p1Ind].getItems();
		_expand(p1Children);
		TreeItem f1Child = _findChild("f1", p1Children);
		assertNotNull("P1 should have a child named f1", f1Child);
		TreeItem[] f1Children = f1Child.getItems();
		assertEquals("f1 folder should have 2 children", 2, f1Children.length);
	}
	
	public void testM2Override() throws Exception {
		_initContent();
		TreeItem[] rootItems = _viewer.getTree().getItems();
		_expand(rootItems);
		TreeItem p2Item = rootItems[_p2Ind];
		TreeItem[] p2Children = p2Item.getItems();
		_expand(p2Children);
		TreeItem file2Child = _findChild("file2.txt", p2Children);
		assertNotNull("P2 should have a child named file2.txt", file2Child);
		assertEquals("file2.txt should be provided by M2 content provider",
				M2File.class, file2Child.getData().getClass());
	}
	/**
	 * Verifies that M1 interceptAdd is called when the resourceContent provider
	 * invokes viewer.add(IResource). As of Galileo, add(IResource) is correctly
	 * pipelined but remove is not.
	 * 
	 * @throws CoreException
	 */
	public void testInterceptAdd() throws CoreException {
		final String NEW_FOLDER_1 = "newFolder1";
		_initContent();