Add additional aria properties to make the thumbnail navigation spec-compliant

src/components/ThumbnailCanvasGrouping.js

@@ -50,6 +50,8 @@ export class ThumbnailCanvasGrouping extends PureComponent {
           width: (Number.isInteger(style.width)) ? style.width - SPACING : null,
         }}
         className={ns('thumbnail-nav-container')}
+        role="gridcell"
+        aria-colindex={index + 1}
       >
         <div
           role="button"

src/components/ThumbnailNavigation.js

@@ -204,6 +204,7 @@ export class ThumbnailNavigation extends Component {
         onKeyUp={this.handleKeyUp}
         role="grid"
       >
+        <div role="row" style={{ height: '100%', width: '100%' }}>
           <AutoSizer
             defaultHeight={100}
             defaultWidth={400}
@@ -223,6 +224,7 @@ export class ThumbnailNavigation extends Component {
               </List>
             )}
           </AutoSizer>
+        </div>
       </Paper>
     );
   }