Add page indicator and progress bar polymer elements

elements/viewer-progress-bar/viewer-progress-bar.html

+<polymer-element name="viewer-progress-bar"
+    attributes="progress text numSegments">
+<template>
+  <link rel="stylesheet" href="viewer-progress-bar.css">
+  <div class="scaler">
+    <ul id="segments"></ul>
+    <div class="center-circle"></div>
+  </div>
+  <div id="text">{{text}}</div>
+</template>
+<script>
+  Polymer('viewer-progress-bar', {
+    progress: 0,
+    text: 'Loading',
+    numSegments: 8,
+    segments: [],
+    ready: function() {
+      this.numSegmentsChanged();
+    },
+    progressChanged: function() {
+      var numVisible = this.progress * this.segments.length / 100.0;
+      for (var i = 0; i < this.segments.length; i++) {
+        this.segments[i].style.visibility =
+            i < numVisible ? 'visible' : 'hidden';
+      }
+
+      if (this.progress >= 100 || this.progress < 0)
+        this.style.opacity = 0;
+    },
+    numSegmentsChanged: function() {
+      // Clear the existing segments.
+      this.segments = [];
+      var segmentsElement = this.$.segments;
+      segmentsElement.innerHTML = '';
+
+      // Create the new segments.
+      var segment = document.createElement('li');
+      segment.classList.add('segment');
+      var angle = 360 / this.numSegments;
+      for (var i = 0; i < this.numSegments; ++i) {
+        var segmentCopy = segment.cloneNode(true);
+        segmentCopy.style.webkitTransform =
+            'rotate(' + (i * angle) + 'deg) skewY(' +
+            -1 * (90 - angle) + 'deg)';
+        segmentsElement.appendChild(segmentCopy);
+        this.segments.push(segmentCopy);
+      }
+      this.progressChanged();
+    }
+  });
+</script>
+</polymer-element>