Support the essential part of Shadow DOM v1

third_party/WebKit/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))
         return attachShadow.apply(null, children);
     return {'isShadowRoot': true,
             'children': children};
 }
 
 // TODO(kochi): This is not pure attachShadow wrapper, but also handles createShadowRoot()
@@ skipping 48 matching lines @@
                 }
             }
             for (var j = 0; j < child.children.length; ++j)
                 shadowRoot.appendChild(child.children[j]);
         } else
             element.appendChild(child);
     }
     return element;
 }
 
+function removeWhiteSpaceOnlyTextNodes(node)
+{
+    for (var i = 0; i < node.childNodes.length; i++) {
+        var child = node.childNodes[i];
+        if (child.nodeType === Node.TEXT_NODE && child.nodeValue.trim().length == 0) {
+            node.removeChild(child);
+            i--;
+        } else if (child.nodeType === Node.ELEMENT_NODE || child.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
+            removeWhiteSpaceOnlyTextNodes(child);
+        }
+    }
+    if (node.shadowRoot) {
+        removeWhiteSpaceOnlyTextNodes(node.shadowRoot);
+    }
+}
+
 function convertTemplatesToShadowRootsWithin(node) {
     var nodes = node.querySelectorAll("template");
     for (var i = 0; i < nodes.length; ++i) {
         var template = nodes[i];
         var mode = template.getAttribute("data-mode");
         var parent = template.parentNode;
         parent.removeChild(template);
         var shadowRoot;
         if (!mode) {
             shadowRoot = parent.createShadowRoot();
@@ skipping 256 matching lines @@
                 return node;
         }
 
         return null;
     };
 
     if (!window.internals)
         return null;
     return iter(root, id);
 }