feat(compiler): added support for host actions

modules/angular2/src/facade/collection.dart

@@ -82,6 +82,9 @@ class StringMapWrapper {
     }
     return m;
   }
+  static List<String> keys(Map<String,dynamic> a) {
+    return a.keys.toList();
+  }
   static bool isEmpty(Map m) => m.isEmpty;
 }
 

modules/angular2/src/facade/collection.ts

@@ -53,6 +53,7 @@ export class StringMapWrapper {
   static contains(map, key) { return map.hasOwnProperty(key); }
   static get(map, key) { return map.hasOwnProperty(key) ? map[key] : undefined; }
   static set(map, key, value) { map[key] = value; }
+  static keys(map) { return Object.keys(map); }
   static isEmpty(map) {
     for (var prop in map) {
       return false;