Protect the changeState calls with the 'changestate' mutex.

renderjs.js

@@ -698,24 +698,8 @@
       return this.element;
     })
     .declareMethod('changeState', function changeState(state_dict) {
-      var next_onStateChange = new RSVP.Queue(),
-        previous_onStateCHange,
-        context = this;
-      if (context.hasOwnProperty('__previous_onStateChange')) {
-        previous_onStateCHange = context.__previous_onStateChange;
-        next_onStateChange
-          .push(function waitForPreviousStateChange() {
-            return previous_onStateCHange;
-          })
-          .push(undefined, function handlePreviousStateChangeError() {
-            // Run callback even if previous failed
-            return;
-          });
-      }
-      context.__previous_onStateChange = next_onStateChange;
-      return next_onStateChange
-        .push(function checkStateModification() {
-          var key,
+      var context = this,
+        key,
         modified = false,
         previous_cancelled = context.hasOwnProperty('__modification_dict'),
         modification_dict;
@@ -744,8 +728,7 @@
             return result;
           });
       }
-        });
-    });
+    }, {mutex: 'changestate'});
 
   /////////////////////////////////////////////////////////////////
   // RenderJSGadget.declareAcquiredMethod