MD Bookmarks: Always use a two-way arrow cursor for resizing the sidebar

chrome/browser/resources/md_bookmarks/app.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 
 <link rel="import" href="chrome://resources/html/cr/ui/splitter.html">
 <link rel="import" href="chrome://bookmarks/api_listener.html">
 <link rel="import" href="chrome://bookmarks/command_manager.html">
 <link rel="import" href="chrome://bookmarks/constants.html">
 <link rel="import" href="chrome://bookmarks/dnd_manager.html">
 <link rel="import" href="chrome://bookmarks/folder_node.html">
 <link rel="import" href="chrome://bookmarks/list.html">
 <link rel="import" href="chrome://bookmarks/router.html">
@@ skipping 16 matching lines @@
 
       #main-container {
         display: flex;
         flex-direction: row;
         flex-grow: 1;
         overflow: auto;
       }
 
       #splitter {
         box-sizing: border-box;
+        cursor: col-resize;
+<if expr="is_win">
+        /* Unlike other platforms, e-resize is a two-way arrow on Windows. */
         cursor: e-resize;
+</if>
         flex: 0 0 var(--splitter-width);
         opacity: 0;
       }
 
       #splitter:hover,
       #splitter.splitter-active {
         -webkit-border-start: 1px solid rgba(0, 0, 0, 0.1);
         opacity: 1;
         transition: opacity 100ms ease-out;
       }
 
-      :host-context([dir='rtl']) #splitter {
-        cursor: w-resize;
-      }
-
       #sidebar {
         -webkit-padding-start: 3px;
         display: block;
         max-width: 40%;
         min-width: var(--min-sidebar-width);
         overflow-x: hidden;
         overflow-y: auto;
         padding-top: 8px;
         user-select: none;
         width: var(--min-sidebar-width);
@@ skipping 11 matching lines @@
       </div>
       <div id="splitter"></div>
       <bookmarks-list></bookmarks-list>
     </div>
     <bookmarks-router></bookmarks-router>
     <bookmarks-command-manager></bookmarks-command-manager>
     <bookmarks-toast-manager duration="5000"></bookmarks-toast-manager>
   </template>
   <script src="chrome://bookmarks/app.js"></script>
 </dom-module>