title: nativeElement.classList.add() alternative
body: <p>I'm trying to create a button component in angular 2.
  At the host I have to set a dynamically generated css classname. (depending on binded property)</p>
  
  <p>'[ngClass]' on host does not work.</p>
  
  <p>I've read that using elementRef.nativeElement.classList.add(value) is not the best way either, because classList is not supported on webworkers (or so)</p>
  
  <p><strong>What are my best options to generate the class dynamically on host?</strong></p>
  
  <pre><code>@Component({
      selector: '[md-button]',
  })
  export class MdButton {
      color_: string;
  
      @Input
      set color() {
          this.color_ = value;
          if (this.elementRef !== undefined) {
              this.elementRef.nativeElement.classList.add('md-' + this.color_);
          }   
      }
  
      get color(): string {
          return this.color_;
      }
  
      constructor(public elementRef: ElementRef){}
  } 
  </code></pre>