Bug 68011 [java search] "Search the JRE System Libraries" looks like a local preference but behaves as a global one... [search]
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/FindReferencesInProjectAction.java
/**
	 * Creates a new <code>FindReferencesInProjectAction</code>. The action 
	 * requires that the selection provided by the site's selection provider is of type 
	 * <code>IStructuredSelection</code>.
	 * 
	 * @param site the site providing context information for this action
	 */
	public FindReferencesInProjectAction(IWorkbenchSite site) {
		super(site);
	}
	/**
	 * Note: This constructor is for internal use only. Clients should not call this constructor.
	 * @param editor the Java editor
	 */
	public FindReferencesInProjectAction(JavaEditor editor) {
		super(editor);
	}
	
	Class[] getValidTypes() {
		return new Class[] { IField.class, IMethod.class, IType.class, ICompilationUnit.class, IPackageDeclaration.class, IImportDeclaration.class, IPackageFragment.class, ILocalVariable.class, ITypeParameter.class };
	}