feat(CSSClass): support binding to classList

Closes #876

modules/angular2/src/directives/class.js

@@ -0,0 +1,37 @@
+import {Decorator} from 'angular2/src/core/annotations/annotations';
+import {isPresent} from 'angular2/src/facade/lang';
+import {DOM} from 'angular2/src/dom/dom_adapter';
+import {NgElement} from 'angular2/src/core/dom/element';
+
+@Decorator({
+  selector: '[class]',
+  bind: {
+    'iterableChanges': 'class | keyValDiff'
+  }
+})
+export class CSSClass {
+  _domEl;
+  constructor(ngEl: NgElement) {
+    this._domEl = ngEl.domElement;
+  }
+
+  _toggleClass(className, enabled) {
+    if (enabled) {
+      DOM.addClass(this._domEl, className);
+    } else {
+      DOM.removeClass(this._domEl, className);
+    }
+  }
+
+  set iterableChanges(changes) {
+    if (isPresent(changes)) {
+      changes.forEachAddedItem((record) => { this._toggleClass(record.key, record.currentValue); });
+      changes.forEachChangedItem((record) => { this._toggleClass(record.key, record.currentValue); });
+      changes.forEachRemovedItem((record) => {
+        if (record.previousValue) {
+          DOM.removeClass(this._domEl, record.key);
+        }
+      });
+    }
+  }
+}