[NTP] Do not reorder if the edit shortcut menu is clicked

Add edit shortcut menu check before starting the reorder flow. This will
prevent the flow from being initiated when the edit shortcut menu is
clicked.

Bug: 851335
Change-Id: I064d3553b52215152671d9d4c1573ca9450dec0a
Reviewed-on: https://chromium-review.googlesource.com/c/1325075Reviewed-by: Mathieu Perreault <mathp@chromium.org>
Commit-Queue: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606282}

chrome/browser/resources/local_ntp/most_visited_single.js

@@ -643,7 +643,9 @@ function setupReorder(tile) {
   // Starts the reorder flow after the user has held the mouse button down for
   // |REORDER_TIMEOUT_DELAY|.
   tile.addEventListener('mousedown', (event) => {
-    if (event.button == 0 /* LEFT CLICK */) {
+    // Do not reorder if the edit menu was clicked.
+    if (event.button == 0 /* LEFT CLICK */ &&
+        !event.target.classList.contains(CLASSES.MD_MENU)) {
       let timeout = -1;
 
       // Cancel the timeout if the user drags the mouse off the tile and