Add options and a browser-action popup.

go-back-with-backspace/content_script.js

-// Listen for shift-backspace or unmodified backspace and navigate if not in
-// an editable field. We capture the event at the Window to let any handlers
-// or listeners registered on the Document have a chance to handle it first.
-window.addEventListener('keydown', function(e) {
+// 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.
+
+// Load the options, then register a keyboard listener.  We capture the event
+// at the Window to let any handlers or listeners registered on the Document
+// have a chance to handle it first.
+var options;
+chrome.storage.sync.get({
+  blacklist: [],
+  disableInApplets: true,
+  whitelist: []
+}, function(items) {
+  options = items;
+  window.addEventListener('keydown', function(e) {
+    handleBackspace(e);
+  });
+});
+
+// Update the local options when they're changed externally.
+chrome.storage.onChanged.addListener(function(changes, area) {
+  if (area === 'sync') {
+    if (changes.blacklist)
+      options.blacklist = changes.blacklist.newValue;
+    if (changes.disableInApplets)
+      options.disableInApplets = changes.disableInApplets.newValue;
+    if (changes.whitelist)
+      options.whitelist = changes.whitelist.newValue;
+  }
+});
+
+// Check for shift-backspace or unmodified backspace and navigate if
+// applicable.
+function handleBackspace(e) {
+  if (e.defaultPrevented ||
+      e.key !== 'Backspace' ||
+      e.altKey ||
+      e.ctrlKey ||
+      e.metaKey)
+    return;
+
+  // The blacklist overrides everything.
+  var url = window.location.href;
+  if (options.blacklist.includes(url))
+    return;
+
+  // The whitelist overrides applet focus.
   // Listening on the Window means the event has no path (see
   // http://crbug.com/645527), so we'll have to look at the focused (active)
   // element. This means it will not work properly with shadow DOM.
   // TODO: Fix behavior with shadow DOM when the above bug is resolved.
-  if (e.key === 'Backspace' &&
-      !e.defaultPrevented &&
-      !e.altKey &&
-      !e.ctrlKey &&
-      !e.metaKey &&
-      !isEditable(document.activeElement)) {
-    e.shiftKey ? window.history.forward(): window.history.back();
-    e.preventDefault();
+  if (!options.whitelist.includes(url) &&
+      disabledInApplet(document.activeElement))
+    return;
+  if (isEditable(document.activeElement))
+    return;
+
+  e.shiftKey ? window.history.forward(): window.history.back();
+  e.preventDefault();
+}
+
+// Return true if the option to diable the extension in applets is enabled, and

[ojan, 2016/09/15 19:07:15]

typo: diable

+// focus is in an embedded Flash or Java applet.
+function disabledInApplet(target) {
+  if (!options.disableInApplets)
+    return false;
+
+  var nodeName = target.nodeName.toUpperCase();
+  var nodeType = target.type || '';
+  nodeType = nodeType.toLowerCase();
+  if ((nodeName === 'EMBED' || nodeName === 'OBJECT') &&
+      (nodeType === 'application/x-shockwave-flash' ||
+       nodeType === 'application/java')) {
+    return true;
   }
-});
+  return false;
+}