feat: remove MapWrapper.create()/get()/set().

Better dart2js code, better Angular code.

modules/angular2/src/facade/collection.dart

@@ -30,17 +30,12 @@ class IterableMap extends IterableBase<List> {
 }
 
 class MapWrapper {
-  static Map create() => {};
   static Map clone(Map m) => new Map.from(m);
   static Map createFromStringMap(Map m) => m;
   static Map createFromPairs(List pairs) => pairs.fold({}, (m, p) {
     m[p[0]] = p[1];
     return m;
   });
-  static get(Map m, k) => m[k];
-  static void set(Map m, k, v) {
-    m[k] = v;
-  }
   static contains(Map m, k) => m.containsKey(k);
   static forEach(Map m, fn(v, k)) {
     m.forEach((k, v) => fn(v, k));

modules/angular2/src/facade/collection.ts

@@ -55,18 +55,15 @@ var _clearValues: {(m: Map<any, any>)} = (function() {
 })();
 
 export class MapWrapper {
-  static create(): Map<any, any> { return new Map(); }
   static clone<K, V>(m: Map<K, V>): Map<K, V> { return createMapFromMap(m); }
   static createFromStringMap(stringMap): Map<string, any> {
-    var result = MapWrapper.create();
+    var result = new Map();
     for (var prop in stringMap) {
-      MapWrapper.set(result, prop, stringMap[prop]);
+      result.set(prop, stringMap[prop]);
     }
     return result;
   }
   static createFromPairs(pairs: List<any>): Map<any, any> { return createMapFromPairs(pairs); }
-  static get<K, V>(m: Map<K, V>, k: K): V { return m.get(k); }
-  static set<K, V>(m: Map<K, V>, k: K, v: V) { m.set(k, v); }
   static contains<K>(m: Map<K, any>, k: K) { return m.has(k); }
   static forEach<K, V>(m: Map<K, V>, fn: /*(V, K) => void*/ Function) { m.forEach(<any>fn); }
   static size(m: Map<any, any>) { return m.size; }