Do not present popup menu if one is already shown

This CL avoid presenting a popup menu is there is already one shown.
This can be done by pressing simultaneously on two buttons.

Bug: 850057
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I3e501235c3527217e9f354277e09bc353430b95b
Reviewed-on: https://chromium-review.googlesource.com/1104694Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568385}

ios/chrome/browser/ui/popup_menu/popup_menu_coordinator.mm

@@ -162,7 +162,9 @@ PopupMenuCommandType CommandTypeFromPopupType(PopupMenuType type) {
 // |guideName|.
 - (void)presentPopupOfType:(PopupMenuType)type
             fromNamedGuide:(GuideName*)guideName {
-  DCHECK(!self.presenter);
+  if (self.presenter)
+    [self dismissPopupMenuAnimated:YES];
+
   id<BrowserCommands> callableDispatcher =
       static_cast<id<BrowserCommands>>(self.dispatcher);
   [callableDispatcher