title: Type 'SafeResourceUrl' is not assignable to type 'string'
body: <p>I am trying to sanitize a pdf url and want to assign it to a string type variable so that I can use it for pdf viewer. Is there any way to do that? 
  If I use <code>any</code> type for pdfSrc type, I am getting <code>Invalid parameter object: need either .data, .range or .url in the &lt;pdf-viewer&gt;</code>. </p>
  
  <p><strong>Note:</strong> The URL which I used is for reference purpose, i would use external URLs in that place</p>
  
  <p><strong>landingpage.component.ts</strong></p>
  
  <pre><code>import { DomSanitizer, SafeResourceUrl, SafeUrl } from '@angular/platform-browser';
  
  export class LandingpageComponent implements OnInit {
       public pdfSrc: string;
  }
  
  constructor(    
      private sanitizer: DomSanitizer) {
  }
  
  fnOpenAsset() {     
     let url = 'http://localhost/pdf_viewer-master/18/docs/pdf.pdf';
     this.pdfSrc = this.sanitizer.bypassSecurityTrustResourceUrl(url);
  }
  </code></pre>
  
  <p><strong>landingpage.component.html</strong></p>
  
  <pre><code>&lt;pdf-viewer class="alignComponentCenter" [src]="pdfSrc" 
  &lt;/pdf-viewer&gt;
  </code></pre>