Add options and a browser-action popup.

go-back-with-backspace/pages/common.js

+// Copyright 2016 Google Inc. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Open a pre-filled email to send feedback to the extension developers. The
+// initial content of the email depends on whether the URL of the current page
+// is provided.
+function reportPage(url) {
+  var subject = chrome.i18n.getMessage('reportSubject');
+  var body = '';
+  if (url)
+    body = chrome.i18n.getMessage('reportBodyWithURL', url);
+  else
+    body = chrome.i18n.getMessage('reportBody');
+  var msg = 'mailto:gobackwithbackspace@google.com' +
+      '?subject=' + encodeURIComponent(subject) +
+      '&body=' + encodeURIComponent(body);
+  chrome.tabs.create({
+    url: msg,
+    active: true});
+}