patch 8.1.2386: 'wincolor' is not used for 'listchars'

Problem:    'wincolor' is not used for 'listchars'.
Solution:   Combine the colors. (closes #5308)
diff --git a/src/testdir/test_highlight.vim b/src/testdir/test_highlight.vim
index c6aa3a2..f63abee 100644
--- a/src/testdir/test_highlight.vim
+++ b/src/testdir/test_highlight.vim
@@ -620,6 +620,28 @@
   call delete('Xtest_wincolor')
 endfunc
 
+func Test_wincolor_listchars()
+  CheckScreendump
+
+  let lines =<< trim END
+	call setline(1, ["one","\t\tsome random text enough long to show 'extends' and 'precedes' includingnbsps, preceding tabs and trailing spaces    ","three"])
+	set wincolor=Todo
+	set nowrap cole=1 cocu+=n
+	set list lcs=eol:$,tab:>-,space:.,trail:_,extends:>,precedes:<,conceal:*,nbsp:#
+	call matchadd('Conceal', 'text')
+	normal 2G5zl
+  END
+  call writefile(lines, 'Xtest_wincolorlcs')
+  let buf = RunVimInTerminal('-S Xtest_wincolorlcs', {'rows': 8})
+
+  call VerifyScreenDump(buf, 'Test_wincolor_lcs', {})
+
+  " clean up
+  call term_sendkeys(buf, "\<Esc>")
+  call StopVimInTerminal(buf)
+  call delete('Xtest_wincolorlcs')
+endfunc
+
 func Test_colorcolumn()
   CheckScreendump