fix race condition in codemirror initialization

over slow connections, iframes don't load fast enough to be ready for code
which depends on certain features existing.

wait until they're ready, then initialize.

www/code/main.js

@@ -8,7 +8,7 @@ define([
     '/customize/pad.js'
     var $ = window.jQuery;
     var ifrw = $('#pad-iframe')[0].contentWindow;
-    var CMeditor = ifrw.CodeMirror;
+    var CMeditor;
 
     $(function () {
         $(window).on('hashchange', function() {
@@ -18,32 +18,50 @@ define([
             window.location.href = window.location.href + '#' + Crypto.genKey();
             return;
         }
-        var key = Crypto.parseKey(window.location.hash.substring(1));
-        var editor = CMeditor.fromTextArea($('#pad-iframe').contents().find('#editor1')[0], {
-          lineNumbers: true,
-          lineWrapping: true,
-          autoCloseBrackets: true,
-          matchBrackets : true,
-          showTrailingSpace : true,
-          styleActiveLine : true,
-          search: true,
-          highlightSelectionMatches: {showToken: /\w+/},
-          extraKeys: {"Ctrl-Q": function(cm){ cm.foldCode(cm.getCursor()); }},
-          foldGutter: true,
-          gutters: ["CodeMirror-linenumbers", "CodeMirror-foldgutter"],
-          mode: "javascript"
-        });
-        editor.setValue(Messages.codeInitialState);
 
-        var rtw =
-            RTWiki.start(ifrw,
-                            Config.websocketURL,
-                            Crypto.rand64(8),
-                            key.channel,
-                            key.cryptKey);
-        editor.on('change', function() {
-            editor.save();
-            rtw.onEvent();
-        });
+        var andThen = function () {
+            var key = Crypto.parseKey(window.location.hash.substring(1));
+            var editor = CMeditor.fromTextArea($('#pad-iframe').contents().find('#editor1')[0], {
+                lineNumbers: true,
+                lineWrapping: true,
+                autoCloseBrackets: true,
+                matchBrackets : true,
+                showTrailingSpace : true,
+                styleActiveLine : true,
+                search: true,
+                highlightSelectionMatches: {showToken: /\w+/},
+                extraKeys: {"Ctrl-Q": function(cm){ cm.foldCode(cm.getCursor()); }},
+                foldGutter: true,
+                gutters: ["CodeMirror-linenumbers", "CodeMirror-foldgutter"],
+                mode: "javascript"
+            });
+            editor.setValue(Messages.codeInitialState);
+
+            var rtw =
+                RTWiki.start(ifrw,
+                                Config.websocketURL,
+                                Crypto.rand64(8),
+                                key.channel,
+                                key.cryptKey);
+            editor.on('change', function() {
+                editor.save();
+                rtw.onEvent();
+            });
+        };
+
+        var interval = 100;
+
+        var first = function () {
+            if (CMeditor = ifrw.CodeMirror) {
+                // it exists, call your continuation
+                andThen();
+            } else {
+                console.log("CMeditor was not defined. Trying again in %sms", interval);
+                // try again in 'interval' ms
+                setTimeout(first, interval);
+            }
+        };
+
+        first();
     });
 });