Use try-finally and ordering to reduce the risk we might generate a blank page.

Author: jcollins-g

lib/resources/script.js

@@ -47,25 +47,29 @@ function saveRightScroll() {
 
 function restoreScrolls() {
   var leftSidebar = document.getElementById('dartdoc-sidebar-left');
-  var leftSidebarX = sessionStorage.getItem('dartdoc-sidebar-left-scrolll');
-  var leftSidebarY = sessionStorage.getItem('dartdoc-sidebar-left-scrollt');
-
   var mainContent = document.getElementById('dartdoc-main-content');
-  var mainContentX = sessionStorage.getItem('dartdoc-main-content-scrolll');
-  var mainContentY = sessionStorage.getItem('dartdoc-main-content-scrollt');
-
   var rightSidebar = document.getElementById('dartdoc-sidebar-right');
-  var rightSidebarX = sessionStorage.getItem('dartdoc-sidebar-right-scrolll');
-  var rightSidebarY = sessionStorage.getItem('dartdoc-sidebar-right-scrollt');
-
-  // Set visibility to visible after scroll to prevent the brief appearance of the
-  // panel in the wrong position.
-  leftSidebar.scrollTo(leftSidebarX, leftSidebarY);
-  leftSidebar.style.visibility = 'visible';
-  mainContent.scrollTo(mainContentX, mainContentY);
-  mainContent.style.visibility = 'visible';
-  rightSidebar.scrollTo(rightSidebarX, rightSidebarY);
-  rightSidebar.style.visibility = 'visible';
+
+  try {
+    var leftSidebarX = sessionStorage.getItem('dartdoc-sidebar-left-scrolll');
+    var leftSidebarY = sessionStorage.getItem('dartdoc-sidebar-left-scrollt');
+
+    var mainContentX = sessionStorage.getItem('dartdoc-main-content-scrolll');
+    var mainContentY = sessionStorage.getItem('dartdoc-main-content-scrollt');
+
+    var rightSidebarX = sessionStorage.getItem('dartdoc-sidebar-right-scrolll');
+    var rightSidebarY = sessionStorage.getItem('dartdoc-sidebar-right-scrollt');
+
+    leftSidebar.scrollTo(leftSidebarX, leftSidebarY);
+    mainContent.scrollTo(mainContentX, mainContentY);
+    rightSidebar.scrollTo(rightSidebarX, rightSidebarY);
+  } finally {
+    // Set visibility to visible after scroll to prevent the brief appearance of the
+    // panel in the wrong position.
+    leftSidebar.style.visibility = 'visible';
+    mainContent.style.visibility = 'visible';
+    rightSidebar.style.visibility = 'visible';
+  }
 }
 
 function initScrollSave() {
@@ -250,9 +254,10 @@ function initSearch(name) {
 }
 
 document.addEventListener("DOMContentLoaded", function() {
+  // Place this first so that unexpected exceptions in other JavaScript do not block page visibility.
+  restoreScrolls();
   hljs.initHighlightingOnLoad();
   initSideNav();
-  restoreScrolls();
   initScrollSave();
   initSearch("search-box");
   initSearch("search-body");