do nothing when trying to reset with the same content which is already present

src/editor/Editor.js

@@ -1047,6 +1047,12 @@ define(function (require, exports, module) {
      * @param {!string} text
      */
     Editor.prototype._resetText = function (text) {
+        var currentText = this._codeMirror.getValue();
+        if (text === currentText) {
+            // there's nothing to reset
+            return;
+        }
+
         var perfTimerName = PerfUtils.markStart("Editor._resetText()\t" + (!this.document || this.document.file.fullPath));
 
         var cursorPos = this.getCursorPos(),

test/spec/Document-test.js

@@ -400,6 +400,24 @@ define(function (require, exports, module) {
                     doc = null;
                 });
             });
+
+            it("should not clean history when reset is called with the same text as in the editor", function () {
+                runs(function () {
+                    promise = CommandManager.execute(Commands.FILE_OPEN, {fullPath: JS_FILE});
+                    waitsForDone(promise, "Open file");
+                });
+                runs(function () {
+                    var doc = DocumentManager.getOpenDocumentForPath(JS_FILE);
+
+                    // Put some text into editor
+                    doc.setText("Foo");
+                    expect(doc._masterEditor._codeMirror.historySize().undo).toBe(1);
+
+                    // Reset text with the same value, expect history not to change
+                    doc.refreshText("Foo", Date.now());
+                    expect(doc._masterEditor._codeMirror.historySize().undo).toBe(1);
+                });
+            });
         });
 
         describe("Refresh and change events", function () {