[Win] Don't show the add/remove desktop shortcut for single users.

If there's a single user in chrome://settings, you can navigate to
chrome://settings/manageProfile to edit it (even though the UI doesn't
always let you). In this case, however, we shouldn't display the add/remove
desktop shortcut button in the manageProfile overlay (since the shortcut for
single users is a non-profile generic Chrome shortcut)

BUG=409735
TEST=Start Chrome. Ensure you only have one profile.
Go to chrome://settings/manageProfile. There shouldn't be an add/remove
shortcut button.

Review URL: https://codereview.chromium.org/542843002

Cr-Commit-Position: refs/heads/master@{#293804}

chrome/browser/ui/webui/options/manage_profile_handler.cc

@@ -459,6 +459,10 @@ void ManageProfileHandler::RequestHasProfileShortcuts(
   if (profile_index == std::string::npos)
     return;
 
+  // Don't show the add/remove desktop shortcut button in the single user case.
+  if (cache.GetNumberOfProfiles() <= 1)
+    return;
+
   const base::FilePath profile_path =
       cache.GetPathOfProfileAtIndex(profile_index);
   ProfileShortcutManager* shortcut_manager =