Gender-neutralize a few more comments / strings.

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 300 matching lines @@
     <message name="IDS_BOOKMARK_MANAGER_INVALID_URL" desc="In Title Case: Error message to display when the user tries to edit or create a bookmark with an invalid URL.">
       Invalid URL.
     </message>
     <message name="IDS_BOOKMARK_MANAGER_RECENT" desc="In Title Case: The label for the tree item that shows the recently added bookmarks.">
       Recent
     </message>
     <message name="IDS_BOOKMARK_MANAGER_SEARCH" desc="In Title Case: The label for the tree item that shows the search results for the bookmarks.">
       Search
     </message>
   </if>
-  <message name="IDS_EXPORT_BOOKMARKS_DEFAULT_FILENAME" desc="Filename that pre-populates the filename field when user attempts to export his bookmarks from Bookmark Manager.">
+  <message name="IDS_EXPORT_BOOKMARKS_DEFAULT_FILENAME" desc="Filename that pre-populates the filename field when user attempts to export their bookmarks from Bookmark Manager.">
     bookmarks_<ph name="DATESTAMP">$1<ex>02_11_11</ex></ph>.html
   </message>
   <!-- End of 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.">
@@ skipping 17 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>