start on observer, not integrated yet.

src/Observer.js

@@ -0,0 +1,57 @@
+ /*
+Copyright 2013 The Polymer Authors. All rights reserved.
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file.
+*/
+
+(function(scope){
+
+var IMPORT_LINK_TYPE = scope.IMPORT_LINK_TYPE;
+var importSelector = 'link[rel=' + IMPORT_LINK_TYPE + ']';
+
+var importer = scope.importer;
+
+function handler(mutations) {
+  for (var i=0, l=mutations.length, m; (i<l) && (m=mutations[i]); i++) {
+    if (m.type === 'childList' && m.addedNodes.length) {
+      addedNodes(m.addedNodes);
+    }
+  });
+};
+
+function addedNodes(nodes) {
+  for (var i=0, l=nodes.length, n; (i<l) && (n=nodes[i]); i++) {
+    if (shouldLoadNode(n)) {
+      // TODO(sorvell): need to add this api.
+      importer.addNode(node);
+    }
+  }
+}
+
+// TODO(sorvell): need x-platform matches
+function shouldLoadNode(node) {
+  return node.matches(importer.preloadSelectors);
+}
+
+var observer = new MutationObserver(handler);
+
+function observe(root) {
+  observer.observe(root, {childList: true, subtree: true});
+}
+
+// *****
+// TODO(sorvell): wip
+function canParse(node) {
+  var doc = node.ownerDocument;
+  return nextImportToParse(doc) === node;
+}
+
+function nextImportToParse(doc) {
+
+}
+
+
+// exports
+scope.observe = observe;
+
+})(HTMLImports);