MD Bookmarks: Add full support for cut/copy/paste keyboard shortcuts

chrome/app/bookmarks_strings.grdp

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Bookmarks specific strings (included from generated_resources.grd). -->
 <grit-part>
   <!-- Begin of Bookmarks Bar strings-->
   <if expr="not is_android">
     <!-- The following two strings are shown when the user has no bookmarks yet. -->
     <message name="IDS_BOOKMARKS_NO_ITEMS" desc="Text shown when the user has no bookmarks">
       For quick access, place your bookmarks here on the bookmarks bar.
     </message>
     <message name="IDS_BOOKMARK_BAR_IMPORT_LINK" desc="text shown for importing ">
@@ skipping 418 matching lines @@
     Folder sorted
   </message>
   <message name="IDS_MD_BOOKMARK_MANAGER_TOAST_ITEMS_DELETED" desc="Label displayed in toast popup message when several items are deleted.">
     {COUNT, plural,
       =1 {'<ph name="DELETED_ITEM_NAME">$1</ph>' has been deleted}
       other {# bookmarks deleted}}
   </message>
   <message name="IDS_MD_BOOKMARK_MANAGER_TOAST_URL_COPIED" desc="Label displayed in toast popup message when a URL is copied.">
     URL copied
   </message>
+  <message name="IDS_MD_BOOKMARK_MANAGER_TOAST_ITEMS_COPIED" desc="Label displayed in a toast popup message when several bookmark items are copied">
+    {COUNT, plural,
+      =1 {'<ph name="COPIED_ITEM_NAME">$1</ph>' copied}
+      other {# items copied}}
+  </message>
   <!-- End of material design Bookmarks Manager strings. -->
 
   <!-- Begin of Bookmarks Menu (in the Main Menu) strings. -->
   <message name="IDS_BOOKMARKS_MENU" desc="The title of the Bookmarks menu in the Main menu and in the Mac menu bar.">
     &amp;Bookmarks
   </message>
   <if expr="not use_titlecase">
     <message name="IDS_BOOKMARK_THIS_PAGE" desc="Title of the menu item that bookmarks the current page.">
       Bookmark this page...
     </message>
@@ skipping 15 matching lines @@
   </if>
   <!-- End of Bookmarks Menu (in the Main Menu) strings. -->
 
   <!-- Begin of Bookmark Star button strings. -->
   <message name="IDS_TOOLTIP_STARRED" desc="The tooltip shown when you hover the star button in the right side of the location bar and the current page is bookmarked.">
     Edit bookmark for this page
   </message>
   <!-- End of Bookmark Star button strings. -->
 
 </grit-part>