Show thumbnail on list view only when the file is image or video.

BUG=402344
TEST=Check that Google doc files don't have thumbnails on list view.

Review URL: https://codereview.chromium.org/899313002

Cr-Commit-Position: refs/heads/master@{#314994}

ui/file_manager/file_manager/foreground/js/ui/file_table.js

@@ -475,7 +475,8 @@ FileTable.prototype.renderName_ = function(entry, columnId, table) {
       (this.ownerDocument.createElement('div'));
 
   var icon = this.renderIconType_(entry, columnId, table);
-  icon.appendChild(this.renderThumbnail_(entry));
+  if (FileType.isImage(entry) || FileType.isVideo(entry))
+    icon.appendChild(this.renderThumbnail_(entry));
   icon.appendChild(this.renderCheckmark_());
   label.appendChild(icon);