Merge reused code into a common file

Change-Id: I264aaa67ae1103df2292e17d1eb46b3054799994
diff --git a/src/options.html b/src/options.html
index 6dc2d46..cd325a0 100644
--- a/src/options.html
+++ b/src/options.html
@@ -23,6 +23,7 @@
     </p>
     <p class="actions"><button id="save" data-i18n="save"></button></p>
     <div id="save-indicator"></div>
+    <script src="common/common.js"></script>
     <script src="options.js"></script>
   </body>
 </html>