DevTools: allow codemirror softundo to work on readonly files

third_party/WebKit/LayoutTests/inspector/editor/editor-test.js

 function initialize_EditorTests()
 {
 
 InspectorTest.createTestEditor = function(clientHeight, textEditorDelegate)
 {
     var textEditor = new WebInspector.CodeMirrorTextEditor("", textEditorDelegate || new WebInspector.TextEditorDelegate());
     clientHeight = clientHeight || 100;
     textEditor.element.style.height = clientHeight + "px";
     textEditor.element.style.flex = "none";
     textEditor.show(WebInspector.inspectorView.element);
@@ skipping 126 matching lines @@
 
 function fakeCodeMirrorInputEvent(editor, character)
 {
     if (typeof character === "string")
         editor._codeMirror.display.input.value += character;
 }
 
 InspectorTest.fakeKeyEvent = function(editor, originalCode, modifiers, callback)
 {
     modifiers = modifiers || [];
+    callback = callback || function() {};
     var code;
     var charCode;
     if (originalCode === "'") {
         code = 222;
         charCode = 0;
     } else if (originalCode === "\"") {
         code = 222;
         modifiers.push("shiftKey");
         charCode = 34;
     } else if (originalCode === "(") {
@@ skipping 42 matching lines @@
         var keyName = sortedKeys[i];
         if (!keyName.length)
             keyName = "<Empty string>";
         else
             keyName = "'" + keyName + "'";
         InspectorTest.addResult(keyName + ": " + listHashMap[sortedKeys[i]]);
     }
 }
 
 }