Allow the PDF page indicator to accept a list of page labels

elements/viewer-page-indicator/viewer-page-indicator.js

Index: elements/viewer-page-indicator/viewer-page-indicator.js
diff --git a/elements/viewer-page-indicator/viewer-page-indicator.js b/elements/viewer-page-indicator/viewer-page-indicator.js
index e22b5a6f91c496e2e3b2ee36080d10bff8527589..8612e170348f1894f46296e0dc5e2be93c984c33 100644
--- a/elements/viewer-page-indicator/viewer-page-indicator.js
+++ b/elements/viewer-page-indicator/viewer-page-indicator.js
@@ -3,8 +3,10 @@
 // found in the LICENSE file.
 
 Polymer('viewer-page-indicator', {
-  text: '1',
+  label: '1',
+  index: 0,
   timerId: undefined,
+  pageLabels: null,
   ready: function() {
     var callback = this.fadeIn.bind(this, 2000);
     window.addEventListener('scroll', function() {
@@ -27,5 +29,14 @@ Polymer('viewer-page-indicator', {
       this.style.opacity = 0;
       this.timerId = undefined;
     }.bind(this), displayTime);
+  },
+  pageLabelsChanged: function() {
+    this.indexChanged();
+  },
+  indexChanged: function() {
+    if (this.pageLabels)
+      this.label = this.pageLabels[this.index];
+    else
+      this.label = String(this.index + 1);
   }
 });