title: matSort not working with multiple mat-tables
body: <p>I have a page with 2 mat-tables populated from 2 data sources. The sorting isn't working for me. Please advise. <a href="https://stackblitz.com/edit/angular-nbx7vk" rel="nofollow noreferrer">Here is the stackblitz link</a></p>
  
  <p>TS File</p>
  
  <pre><code>export class TableSortingExample implements OnInit {
    displayedColumns: string[] = ['position', 'name', 'weight', 'symbol'];
    displayedColumns2: string[] = ['position2', 'name2', 'weight2'];
    dataSource = new MatTableDataSource(ELEMENT_DATA);
    dataSource2 = new MatTableDataSource(ELEMENT_DATA2);
  
     @ViewChildren(MatSort)
    sort = new QueryList&lt;MatSort&gt;();
  
    ngOnInit() {
      this.dataSource.sort = this.sort.toArray()[0];
      this.dataSource2.sort = this.sort.toArray()[1];
    }
  }
  </code></pre>
  
  <p>I couldn't put the html file here, stackoverflow said too much code in question. Please go over to the stackblitz to see the html.</p>