fix: remove one more use of for..of

modules/angular2/src/change_detection/parser/context_with_variable_bindings.js

@@ -31,8 +31,6 @@ export class ContextWithVariableBindings {
   }
 
   clearValues() {
-    for (var k of MapWrapper.keys(this.varBindings)) {
-      MapWrapper.set(this.varBindings, k, null);
-    }
+    MapWrapper.clearValues(this.varBindings);
   }
 }

modules/angular2/src/facade/collection.dart

@@ -52,6 +52,11 @@ class MapWrapper {
   static void clear(Map m) {
     m.clear();
   }
+  static void clearValues(Map m) {
+    for (var k in m.keys) {
+      m[k] = null;
+    }
+  }
   static Iterable iterable(Map m) => new IterableMap(m);
   static Iterable keys(Map m) => m.keys;
   static Iterable values(Map m) => m.values;

modules/angular2/src/facade/collection.es6

@@ -25,6 +25,13 @@ export class MapWrapper {
   static size(m) {return m.size;}
   static delete(m, k) { m.delete(k); }
   static clear(m) { m.clear(); }
+  static clearValues(m) {
+    var keyIterator = m.keys();
+    var k;
+    while (!((k = keyIterator.next()).done)) {
+      m.set(k.value, null);
+    }
+  }
   static iterable(m) { return m; }
   static keys(m) { return m.keys(); }
   static values(m) { return m.values(); }