Bug 49182 What should canceling setRawClasspath do ?
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/BuildPathsPropertyPage.java
private static final String PAGE_SETTINGS= "BuildPathsPropertyPage"; 
	private static final String INDEX= "pageIndex"; 
		
	private BuildPathsBlock fBuildPathsBlock;
	
	/*
	 * @see PreferencePage#createControl(Composite)
	 */
	protected Control createContents(Composite parent) {
		
		noDefaultAndApplyButton();		
		
		IProject project= getProject();
		Control result;
		if (project == null || !isJavaProject(project)) {
			result= createWithoutJava(parent);
		} else if (!project.isOpen()) {
			result= createForClosedProject(parent);
		} else {
			result= createWithJava(parent, project);
		}
		Dialog.applyDialogFont(result);
		return result;
	}