Files app: Wrap <cr-menu> tags in a <menus> tag

This makes easier to navigate in the DOM when using the DevTools,
because the list of <cr-menu>'s is too long distracting from the main
part of the Files app content.

Bug: 992821
Change-Id: I1833a3742bfa6fd8329c27f43bfbf65bf318e649
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2026510
Commit-Queue: Noel Gordon <noel@chromium.org>
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736255}

ui/file_manager/file_manager/main.html

@@ -189,6 +189,7 @@
       <command id="focus-action-bar" shortcut="a|Alt">
     </commands>
 
+    <menus>
       <cr-menu id="disabled-context-menu" class="chrome-menu files-menu">
       </cr-menu>
 
@@ -350,6 +351,7 @@
       <cr-menu id="share-sub-menu" class="chrome-menu files-menu"
                menu-item-selector="cr-menu-item">
       </cr-menu>
+    </menus>
 
     <div class="dialog-header" role="contentinfo">
       <div id="location-breadcrumbs" class="breadcrumbs"></div>