patch 9.0.0507: cmdline cleared when using :redrawstatus in CmdlineChanged

Problem:    Command line cleared when using :redrawstatus in CmdlineChanged
            autocommand event.
Solution:   Postpone the redraw. (closes #11162)
diff --git a/src/testdir/test_cmdline.vim b/src/testdir/test_cmdline.vim
index 27ca8bf..3014ac3 100644
--- a/src/testdir/test_cmdline.vim
+++ b/src/testdir/test_cmdline.vim
@@ -210,6 +210,25 @@
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_redrawstatus_in_autocmd()
+  CheckScreendump
+
+  let lines =<< trim END
+      set cmdheight=2
+      autocmd CmdlineChanged * if getcmdline() == 'foobar' | redrawstatus | endif
+  END
+  call writefile(lines, 'XTest_redrawstatus', 'D')
+
+  let buf = RunVimInTerminal('-S XTest_redrawstatus', {'rows': 8})
+  call term_sendkeys(buf, ":echo \"one\\ntwo\\nthree\\nfour\"\<CR>")
+  call term_sendkeys(buf, ":foobar")
+  call VerifyScreenDump(buf, 'Test_redrawstatus_in_autocmd_1', {})
+
+  " clean up
+  call term_sendkeys(buf, "\<CR>")
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_changing_cmdheight()
   CheckScreendump