refactor(template loading): add support for base URLs, css rewriting

fixes #654

modules/angular2/src/facade/dom.dart

@@ -11,9 +11,11 @@ export 'dart:html' show
   Element,
   location,
   Node,
+  ShadowRoot,
   StyleElement,
   TemplateElement,
   InputElement,
+  AnchorElement,
   Text,
   window;
 
@@ -127,6 +129,8 @@ class DOM {
     el.text = css;
     return el;
   }
+  static ShadowRoot createShadowRoot(Element el) => el.createShadowRoot();
+  static ShadowRoot getShadowRoot(Element el) => el.shadowRoot;
   static clone(Node node) => node.clone(true);
   static bool hasProperty(Element element, String name) =>
       new JsObject.fromBrowserObject(element).hasProperty(name);

modules/angular2/src/facade/dom.es6

@@ -6,8 +6,10 @@ export var Node = window.Node;
 export var NodeList = window.NodeList;
 export var Text = window.Text;
 export var Element = window.HTMLElement;
+export var AnchorElement = window.HTMLAnchorElement;
 export var TemplateElement = window.HTMLTemplateElement;
 export var StyleElement = window.HTMLStyleElement;
+export var ShadowRoot = window.ShadowRoot;
 export var document = window.document;
 export var location = window.location;
 export var gc = window.gc ? () => window.gc() : () => null;
@@ -144,6 +146,12 @@ export class DOM {
     style.innerText = css;
     return style;
   }
+  static createShadowRoot(el: Element): ShadowRoot {
+    return el.createShadowRoot();
+  }
+  static getShadowRoot(el: Element): ShadowRoot {
+    return el.shadowRoot;
+  }
   static clone(node:Node) {
     return node.cloneNode(true);
   }