message: Fix position of close icon after angular upgrade
diff: <mat-toolbar matDialogTitle role="header">
  + <mat-toolbar-row>
  <span>Fullscreen Mode</span>
  <span class="toolbar-fill"></span>
  <button mat-mini-fab color="primary" (click)="onCloseClick()" matTooltip="Quit Fullscreen">
  <mat-icon>close</mat-icon>
  </button>
  + </mat-toolbar-row>
  </mat-toolbar>
  <app-free-text-unit-editor [(markdown)]="data.markdown"></app-free-text-unit-editor>
  