Fix open all tabs in about:bookmarks on toolbar

Fix #3614

Auditors: @aekeus

Since this can cause the browser to
hang with a ton of tabs, when it's a lot of tabs I only load the first
30 as loaded tabs.

Test Plan:
Go into about:bookmarks and open in all tabs on the toolbar.
Make sure it works.
Then do the same for some
other folder, make sure it works.  Then test with > 30 items and make
sure only the first 30 show up loaded

js/actions/bookmarkActions.js

@@ -11,10 +11,13 @@ const eventUtil = require('../lib/eventUtil.js')
 const bookmarkActions = {
   openBookmarksInFolder: function (allBookmarkItems, folderDetail) {
     // We have a middle clicked folder
-    allBookmarkItems
-      .filter((bookmark) => bookmark.get('parentFolderId') === folderDetail.get('folderId') && siteUtil.isBookmark(bookmark))
-      .forEach((bookmark) =>
-        windowActions.newFrame(siteUtil.toFrameOpts(bookmark), false))
+    const bookmarks = allBookmarkItems
+      .filter((bookmark) => (bookmark.get('parentFolderId') || 0) === (folderDetail.get('folderId') || 0) && siteUtil.isBookmark(bookmark))
+
+    // Only load the first 25 tabs as loaded
+    bookmarks
+      .forEach((bookmark, i) =>
+        windowActions.newFrame(Object.assign(siteUtil.toFrameOpts(bookmark), {unloaded: i > 25}), false))
   },
 
   /**

js/contextMenus.js

@@ -267,8 +267,10 @@ function siteDetailTemplateInit (siteDetail, activeFrame) {
   }
 
   if (!isHistoryEntry) {
+    if (template[template.length - 1] !== CommonMenu.separatorMenuItem) {
+      template.push(CommonMenu.separatorMenuItem)
+    }
     template.push(
-      CommonMenu.separatorMenuItem,
       addBookmarkMenuItem('addBookmark', siteUtil.getDetailFromFrame(activeFrame, siteTags.BOOKMARK), siteDetail, true),
       addFolderMenuItem(siteDetail, true))
   }