Update UI and catch executeScript errors now shown in Canary

go-back-with-backspace/content_script.js

Index: go-back-with-backspace/content_script.js
diff --git a/go-back-with-backspace/content_script.js b/go-back-with-backspace/content_script.js
index cc7fca6218a17ebc7f28b84725daee28d3925a22..c462d5b72188c17320e904d9b4afb98dad8f4bfb 100644
--- a/go-back-with-backspace/content_script.js
+++ b/go-back-with-backspace/content_script.js
@@ -44,14 +44,16 @@ function handleBackspace(e) {
     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.
@@ -78,9 +80,10 @@ function handleBackspace(e) {
 }
 
 // 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();