From 50b719379f50934757a9ac932cdfc67c056f4c5c Mon Sep 17 00:00:00 2001
From: Tim Taubert <ttaubert@mozilla.com>
Date: Thu, 21 Mar 2013 09:23:02 +0100
Subject: [PATCH] Bug 851845 - Intermittent (NS_ERROR_NOT_AVAILABLE)
 [nsIDOMWindowUtils.getScrollbarSize]; r=jaws

---
 toolkit/components/thumbnails/PageThumbs.jsm | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/toolkit/components/thumbnails/PageThumbs.jsm b/toolkit/components/thumbnails/PageThumbs.jsm
index 31a5de704f0d..9200d6bea74f 100644
--- a/toolkit/components/thumbnails/PageThumbs.jsm
+++ b/toolkit/components/thumbnails/PageThumbs.jsm
@@ -244,7 +244,14 @@ this.PageThumbs = {
     let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
                        .getInterface(Ci.nsIDOMWindowUtils);
     let sbWidth = {}, sbHeight = {};
-    utils.getScrollbarSize(false, sbWidth, sbHeight);
+
+    try {
+      utils.getScrollbarSize(false, sbWidth, sbHeight);
+    } catch (e) {
+      // This might fail if the window does not have a presShell.
+      Cu.reportError("Unable to get scrollbar size in _determineCropSize.");
+      sbWidth.value = sbHeight.value = 0;
+    }
 
     // Even in RTL mode, scrollbars are always on the right.
     // So there's no need to determine a left offset.