feat(ComponentUrlMapper): retrieve the base URL for components

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

@@ -0,0 +1,31 @@
+import {Type, isPresent} from 'angular2/src/facade/lang';
+import {Map, MapWrapper} from 'angular2/src/facade/lang';
+
+export class ComponentUrlMapper {
+  // Returns the url to the component source file.
+  // The returned url could be:
+  // - an absolute URL,
+  // - a URL relative to the application
+  getUrl(component: Type): string {
+    return './';
+  }
+}
+
+export class RuntimeComponentUrlMapper extends ComponentUrlMapper {
+  _componentUrls: Map;
+
+  constructor() {
+    super();
+    this._componentUrls = MapWrapper.create();
+  }
+
+  setComponentUrl(component: Type, url: string) {
+    MapWrapper.set(this._componentUrls, component, url);
+  }
+
+  getUrl(component: Type): string {
+    var url = MapWrapper.get(this._componentUrls, component);
+    if (isPresent(url)) return url;
+    return super.getUrl(component);
+  }
+}