update demo so startProgress will call nextProgress only if it's not

animating

Author: frankiefu

demo.html

@@ -62,13 +62,15 @@
     var progress = document.querySelector('paper-progress');
     var button = document.querySelector('paper-button');
 
-    var repeat, maxRepeat = 5;
+    var repeat, maxRepeat = 5, animating = false;
 
     function nextProgress() {
+      animating = true;
       if (progress.value < progress.max) {
         progress.value += (progress.step || 1);
       } else {
         if (++repeat >= maxRepeat) {
+          animating = false;
           button.disabled = false;
           return;
         }
@@ -81,7 +83,9 @@
       repeat = 0;
       progress.value = progress.min;
       button.disabled = true;
-      nextProgress();
+      if (!animating) {
+        nextProgress();
+      }
     }
 
     addEventListener('polymer-ready', function() {