Merge pull request #3814 from tsl0922/fix-ace-mode-404

fix ace editor Syntax Highlighter mode load 404

app/views/edit_tree/show.html.haml

@@ -30,6 +30,7 @@
       = link_to "Cancel", project_tree_path(@project, @id), class: "btn btn-cancel", confirm: "Are you sure?"
 
 :javascript
+  ace.config.set("modePath", "#{Gitlab::Application.config.assets.prefix}/ace-src-noconflict")
   var ace_mode = "#{@blob.language.try(:ace_mode)}";
   var editor = ace.edit("editor");
   if (ace_mode) {