feat(UrlResolver): combine a base URL with an URL

modules/angular2/src/core/compiler/url_resolver.js

@@ -0,0 +1,36 @@
+import {isPresent, isBlank, RegExpWrapper} from 'angular2/src/facade/lang';
+import {DOM, Element} from 'angular2/src/facade/dom';
+
+export class UrlResolver {
+  static a: Element;
+
+  constructor() {
+    if (isBlank(UrlResolver.a)) {
+      UrlResolver.a = DOM.createElement('a');
+    }
+  }
+
+  resolve(baseUrl: string, url: string): string {
+    if (isBlank(baseUrl)) {
+      UrlResolver.a.href = url;
+      return UrlResolver.a.href;
+    }
+
+    if (isBlank(url) || url == '') return baseUrl;
+
+    if (url[0] == '/') {
+      throw new BaseException(`Could not resolve the url ${url} from ${baseUrl}`);
+    }
+
+    var m = RegExpWrapper.firstMatch(_schemeRe, url);
+
+    if (isPresent(m[1])) {
+      return url;
+    }
+
+    UrlResolver.a.href = baseUrl + '/../' + url;
+    return UrlResolver.a.href;
+  }
+}
+
+var _schemeRe = RegExpWrapper.create('^([^:/?#]+:)?');