Bug 12802 modify parameters: should be enabled if a parameter is selected in the editor [refactoring]
currently, you have to select a method
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/ModifyParametersAction.java
private ModifyParametersRefactoring fRefactoring;
	private CompilationUnitEditor fEditor;
	
	/**
	 * Note: This constructor is for internal use only. Clients should not call this constructor.
	 */
	public ModifyParametersAction(CompilationUnitEditor editor) {
		this(editor.getEditorSite());
		fEditor= editor;
		setEnabled(SelectionConverter.canOperateOn(fEditor));
	}
	/**
	 * Creates a new <code>ModifyParametersAction</code>. The action requires
	 * that the selection provided by the site's selection provider is of type <code>
	 * org.eclipse.jface.viewers.IStructuredSelection</code>.
	 * 
	 * @param site the site providing context information for this action
	 */
	public ModifyParametersAction(IWorkbenchSite site) {
		super(site);
		setText(RefactoringMessages.getString("RefactoringGroup.modify_Parameters_label"));
		WorkbenchHelp.setHelp(this, IJavaHelpContextIds.MODIFY_PARAMETERS_ACTION);