Add menu on GUIEnter

Thanks @thinca
http://lingr.com/room/vim/archives/2016/02/20#message-23060349

plugin/openbrowser.vim

@@ -246,19 +246,26 @@ xnoremap <silent> <Plug>(openbrowser-smart-search) :<C-u>call openbrowser#_keyma
 
 " Popup menus for Right-Click
 if !get(g:, 'openbrowser_no_default_menus', (&guioptions =~# 'M'))
-    if get(g:, 'openbrowser_menu_lang',
-    \      &langmenu !=# '' ? &langmenu : v:lang) =~# '^ja'
-        runtime! lang/openbrowser_menu_ja.vim
-    endif
+    function! s:add_menu() abort
+        if get(g:, 'openbrowser_menu_lang',
+        \      &langmenu !=# '' ? &langmenu : v:lang) =~# '^ja'
+            runtime! lang/openbrowser_menu_ja.vim
+        endif
+
+        nnoremenu PopUp.-OpenBrowserSep- <Nop>
+        xnoremenu PopUp.-OpenBrowserSep- <Nop>
+        nmenu <silent> PopUp.Open\ URL <Plug>(openbrowser-open)
+        xmenu <silent> PopUp.Open\ URL <Plug>(openbrowser-open)
+        nmenu <silent> PopUp.Open\ Word(s) <Plug>(openbrowser-search)
+        xmenu <silent> PopUp.Open\ Word(s) <Plug>(openbrowser-search)
+        nmenu <silent> PopUp.Open\ URL\ or\ Word(s) <Plug>(openbrowser-smart-search)
+        xmenu <silent> PopUp.Open\ URL\ or\ Word(s) <Plug>(openbrowser-smart-search)
+    endfunction
 
-    nnoremenu PopUp.-OpenBrowserSep- <Nop>
-    xnoremenu PopUp.-OpenBrowserSep- <Nop>
-    nmenu <silent> PopUp.Open\ URL <Plug>(openbrowser-open)
-    xmenu <silent> PopUp.Open\ URL <Plug>(openbrowser-open)
-    nmenu <silent> PopUp.Open\ Word(s) <Plug>(openbrowser-search)
-    xmenu <silent> PopUp.Open\ Word(s) <Plug>(openbrowser-search)
-    nmenu <silent> PopUp.Open\ URL\ or\ Word(s) <Plug>(openbrowser-smart-search)
-    xmenu <silent> PopUp.Open\ URL\ or\ Word(s) <Plug>(openbrowser-smart-search)
+    augroup openbrowser-menu
+        autocmd!
+        autocmd GUIEnter * call s:add_menu()
+    augroup END
 endif
 
 " }}}