Add block name as JSON id.

core/field_textinput.js

@@ -258,10 +258,13 @@ Blockly.FieldTextInput.prototype.widgetDispose_ = function() {
     // Save the edit (if it validates).
     var text = htmlInput.value;
     if (thisField.sourceBlock_ && thisField.changeHandler_) {
-      text = thisField.changeHandler_(text);
-      if (text === null) {
+      var text1 = thisField.changeHandler_(text);
+      if (text1 === null) {
         // Invalid edit.
         text = htmlInput.defaultValue;
+      } else if (text1 !== undefined) {
+        // Change handler has changed the text.
+        text = text1;
       }
     }
     thisField.setText(text);

demos/blockfactory/factory.js

@@ -82,6 +82,8 @@ function updateLanguage() {
  */
 function formatJson(code, rootBlock) {
   var JS = {};
+  // ID is not used by Blockly, but may be used by a loader.
+  JS.id = blockType;
   // Generate inputs.
   var message = [];
   var args = [];