Update UI and catch executeScript errors now shown in Canary

go-back-with-backspace/content_script.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.
 
 // 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: [],
@@ skipping 26 matching lines @@
       e.metaKey ||
       window.history.length < 2) // Nowhere to go back or forward to anyway.
     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 (!options.whitelist.includes(url) &&
-      disabledInApplet(document.activeElement))
+  // Before Chrome 55, listening on the Window means the event has no path,
+  // instead pointing to the Window (see http://crbug.com/645527). In that
+  // case, we have to look at the focused (active) element.
+  // TODO: Switch entirely to e.path once Chrome 55 is launched.
+  var target = e.path[0];
+  if (target === window)
+    target = document.activeElement;
+  if (disabledInApplet(url, target))
     return;
-  if (isEditable(document.activeElement))
+  if (isEditable(target))
     return;
 
   // Make sure this extension is still active.
   // sendMessage throws an internal error, not reported in lastError, if the
   // other end no longer exists. So we use JS error-catching rather than
   // extension errors. See http://crbug.com/650872
   try {
     chrome.runtime.sendMessage('', function(response) {
       // Future-proofing in case sendMessage ever changes to setting lastError
       // instead of throwing a JS error.
       if (chrome.runtime.lastError) {
         window.removeEventListener('keydown', handleBackspace);
       } else {
         e.shiftKey ? window.history.forward(): window.history.back();
         e.preventDefault();
       }
     });
   } catch(error) {
     // If we have no connection to the background page, the extension has
     // been updated, disabled, or uninstalled. Remove our listener and do
     // nothing.
     window.removeEventListener('keydown', handleBackspace);
   }
 }
 
 // Return true if the option to disable the extension in applets is enabled,
-// and focus is in an embedded Flash or Java applet.
-function disabledInApplet(target) {
-  if (!options.disableInApplets)
+// focus is in an embedded Flash or Java applet, and the current page is not
+// in the whitelist of pages for which that should not apply.
+function disabledInApplet(url, target) {
+  if (!options.disableInApplets || options.whitelist.includes(url))
     return false;
 
   var nodeName = target.nodeName.toUpperCase();
   var nodeType = target.type || '';
   nodeType = nodeType.toLowerCase();
   if ((nodeName === 'EMBED' || nodeName === 'OBJECT') &&
       (nodeType === 'application/java' ||
        nodeType === 'application/pdf' ||
        nodeType === 'application/x-chat' ||
        nodeType === 'application/x-google-chrome-pdf' ||
        nodeType === 'application/x-shockwave-flash')) {
     return true;
   }
   return false;
 }