Add the Quickoffice viewer toolbar polymer elements.

elements/viewer-button/viewer-button.html

Index: elements/viewer-button/viewer-button.html
diff --git a/elements/viewer-button/viewer-button.html b/elements/viewer-button/viewer-button.html
new file mode 100644
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+++ b/elements/viewer-button/viewer-button.html
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+<polymer-element name="viewer-button" attributes="src latchable">
+  <template>
+    <link rel="stylesheet" href="viewer-button.css">
+    <div id="icon"></div>
+  </template>
+  <script>
+    (function() {
+    var dpi = '';
+
+    Polymer('viewer-button', {
+      src: '',
+      latchable: false,
+      ready: function() {
+        if (!dpi) {
+          var mql = window.matchMedia('(-webkit-min-device-pixel-ratio: 1.3');
+          dpi = mql.matches ? 'hi' : 'low';
+        }
+      },
+      srcChanged: function() {
+        if (this.src) {
+          this.$.icon.style.backgroundImage =
+              'url(elements/viewer-button/img/' + dpi + 'DPI/' + this.src + ')';
+        } else {
+          this.$.icon.style.backgroundImage = '';
+        }
+      },
+      latchableChanged: function() {
+        if (this.latchable)
+          this.classList.add('latchable');
+        else
+          this.classList.remove('latchable');
+      },
+    });
+    })();
+  </script>
+</polymer-element>