Mutations in block representation; an unfeatured procedure call (#212)

* Add scratch3_procedures and no-op for defnoreturn

* Add mutation adapter to parse mutations in CREATE/CHANGE events

* Add mutation-to-XML

* Update spec map for Blockly procedure names

* Placeholder for procedure special cases

* Basic stepping to procedures

* Remove extra case

* Validation for changeBlock

src/engine/sequencer.js

@@ -124,6 +124,16 @@ Sequencer.prototype.stepToBranch = function (thread, branchNum) {
     }
 };
 
+/**
+ * Step a procedure.
+ * @param {!Thread} thread Thread object to step to procedure.
+ * @param {!string} procedureName Name of procedure defined in this target.
+ */
+Sequencer.prototype.stepToProcedure = function (thread, procedureName) {
+    var definition = thread.target.blocks.getProcedureDefinition(procedureName);
+    thread.pushStack(definition);
+};
+
 /**
  * Step a thread into an input reporter, and manage its status appropriately.
  * @param {!Thread} thread Thread object to step to reporter.