feat(NgStyle): add new NgStyle directive

Closes #2665

modules/angular2/src/directives/ng_style.ts

@@ -0,0 +1,38 @@
+import {Directive, onCheck} from 'angular2/annotations';
+import {ElementRef} from 'angular2/core';
+import {Pipe} from 'angular2/src/change_detection/pipes/pipe';
+import {PipeRegistry} from 'angular2/src/change_detection/pipes/pipe_registry';
+import {KeyValueChanges} from 'angular2/src/change_detection/pipes/keyvalue_changes';
+import {isPresent, print} from 'angular2/src/facade/lang';
+import {Renderer} from 'angular2/src/render/api';
+
+@Directive({selector: '[ng-style]', lifecycle: [onCheck], properties: ['rawStyle: ng-style']})
+export class NgStyle {
+  _pipe: Pipe;
+  _rawStyle;
+
+  constructor(private _pipeRegistry: PipeRegistry, private _ngEl: ElementRef,
+              private _renderer: Renderer) {}
+
+  set rawStyle(v) {
+    this._rawStyle = v;
+    this._pipe = this._pipeRegistry.get('keyValDiff', this._rawStyle);
+  }
+
+  onCheck() {
+    var diff = this._pipe.transform(this._rawStyle);
+    if (isPresent(diff) && isPresent(diff.wrapped)) {
+      this._applyChanges(diff.wrapped);
+    }
+  }
+
+  private _applyChanges(diff: KeyValueChanges): void {
+    diff.forEachAddedItem((record) => { this._setStyle(record.key, record.currentValue); });
+    diff.forEachChangedItem((record) => { this._setStyle(record.key, record.currentValue); });
+    diff.forEachRemovedItem((record) => { this._setStyle(record.key, null); });
+  }
+
+  private _setStyle(name: string, val: string): void {
+    this._renderer.setElementStyle(this._ngEl, name, val);
+  }
+}