Don't try to load favicon.ico for error pages. b=453442 r=gavin

browser/base/content/browser.js

@@ -2697,8 +2697,10 @@ const BrowserSearch = {
     }
 
     // Append the URI and an appropriate title to the browser data.
+    // Use documentURIObject in the check for shouldLoadFavIcon so that we
+    // do the right thing with about:-style error pages.  Bug 453442
     var iconURL = null;
-    if (gBrowser.shouldLoadFavIcon(browser.currentURI))
+    if (gBrowser.shouldLoadFavIcon(browser.contentDocument.documentURIObject))
       iconURL = browser.currentURI.prePath + "/favicon.ico";
 
     var hidden = false;

browser/base/content/tabbrowser.xml

@@ -602,7 +602,9 @@
                 } catch (e) { }
               }
             }
-            else if (this.shouldLoadFavIcon(browser.currentURI)) {
+            // Use documentURIObject in the check for shouldLoadFavIcon so that we
+            // do the right thing with about:-style error pages.  Bug 453442
+            else if (this.shouldLoadFavIcon(browser.contentDocument.documentURIObject)) {
               var url = browser.currentURI.prePath + "/favicon.ico";
               if (!this.isFailedIcon(url))
                 this.setIcon(aTab, url);

browser/components/sidebar/src/nsSidebar.js

@@ -205,7 +205,11 @@ function (aDescriptionURL)
   var win = WINMEDSVC.getMostRecentWindow("navigator:browser");
   var browser = win.document.getElementById("content");
   var iconURL = "";
-  if (browser.shouldLoadFavIcon(browser.selectedBrowser.currentURI))
+  // Use documentURIObject in the check for shouldLoadFavIcon so that we
+  // do the right thing with about:-style error pages.  Bug 453442
+  if (browser.shouldLoadFavIcon(browser.selectedBrowser
+                                       .contentDocument
+                                       .documentURIObject))
     iconURL = win.gProxyFavIcon.getAttribute("src");
   
   if (!this.validateSearchEngine(aDescriptionURL, iconURL))