Update UI and catch executeScript errors now shown in Canary

go-back-with-backspace/pages/popup.css

 /**
  * 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.
  */
 
 body {
   direction: __MSG_@@bidi_dir__;
-  width: 300px;
+  width: 270px;
+  text-align: center;
+  margin: 0;
 }
 
-#list_edit_button, #messages  {
+h1 {
+  margin-__MSG_@@bidi_start_edge__: 8px;
+  margin-top: 4px;
+  font-size: 17px;
+  text-align: left;
+}
+
+.bottom-bar {
+  align-items: center;
+  background-color: #f1f1f1;
+  border-top: 1px solid #ccc;
+  height: 33px;
+  padding: 0 5px;
+  margin-top: 2px;
+}
+
+.bottom-bar > span {
+  padding-top: 5px;
+}
+
+.button-image {
+  cursor: pointer;
+  outline: none;
+  background-position: center;
+  background-repeat: no-repeat;
+  background-size: 20px 20px;
+  opacity: .54;
+  height: 24px;
+  width: 24px;
+}
+
+#list-edit-button {
+  height: 30px;
+  line-height: 30px;
+  background-image: -webkit-linear-gradient(top, #4d90fe, #4787ed);
+  border: 1px solid #3079ed;
+  border-radius: 2px;
+  color: white;
+  display: inline-block;
+  font-size: 13px;
+  padding: 0 8px 0 8px;
   margin-bottom: 10px;
 }
 
-#list_edit_button {
-  margin-top: 10px;
+#list-edit-button:hover:enabled {
+  background-image: -webkit-linear-gradient(top, #4d90fe ,#357ae8);
+  border: 1px solid #2f5bb7;
 }
 
-#current_url {
-  text-overflow: ellipsis;
-  white-space: nowrap;
-  overflow: hidden;
+#list-edit-button:disabled {
+  opacity: 0.5;
+}
+
+#file-url-message {
+  margin-bottom: 5px;
 }
 
 #status {
   color: green;
+  line-height: 33px;
 }
 
 #status.error {
   color: red;
 }
 
-#report_page {
+#feedback-button {
   float: __MSG_@@bidi_start_edge__;
 }
 
-#open_options {
+#options-button {
   float: __MSG_@@bidi_end_edge__;
 }