Implement ShadowRoot.delegatesFocus 1/4 (focus navigation)

LayoutTests/fast/dom/shadow/resources/shadow-dom.js

 function createShadowRoot()
 {
     var children = Array.prototype.slice.call(arguments);
     if ((children[0] instanceof Object) && !(children[0] instanceof Node)) {
         var attributes = {};
         var parameter = {};
         for (var key in children[0]) {
-            if (key == 'mode')
+            if (key == 'mode' || key == 'delegatesFocus')
                 parameter[key] = children[0][key];
             else
                 attributes[key] = children[0][key];
         }
         return {'isShadowRoot': true,
                 'parameter': parameter,
                 'attributes': attributes,
                 'children': children.slice(1)};
     }
     return {'isShadowRoot': true,
@@ skipping 253 matching lines @@
     debug('Traverse in backward.');
     showComposedShadowTreeByTraversingInBackward(node);
 
     debug('');
 }
 
 function showNextNode(node) {
     var next = internals.nextInComposedTree(node);
     debug('Next node of [' + dumpNode(node) + '] is [' + dumpNode(next) + ']');
 }