Reinstate comment removed during refactor

CL:1490354 removed a touch-mode flag. As part of that removal, a
potentially useful comment was removed.

Reinstate the removed comment.

Bug: 934467
No-try: true
Change-Id: If4ed10e4361d27d115137ad7e90d5c569bc183a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321911Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#792175}

ui/file_manager/file_manager/foreground/js/ui/list_container.js

@@ -121,6 +121,8 @@ class ListContainer {
     this.element.addEventListener(
         'contextmenu', this.onContextMenu_.bind(this), /* useCapture */ true);
 
+    // Disables context menu by long-tap when at least one file/folder is
+    // selected, while still enabling two-finger tap.
     this.element.addEventListener('touchstart', function(e) {
       if (e.touches.length > 1) {
         this.allowContextMenuByTouch_ = true;