From 2861d35c4b79215cca1abe229833b9cf212d0897 Mon Sep 17 00:00:00 2001
From: Botond Ballo <botond@mozilla.com>
Date: Fri, 1 Sep 2017 13:19:56 -0400
Subject: [PATCH] Bug 1393424 - Don't try to autoscroll in Print Preview mode.
 r=kats

It doesn't work properly anyways due to a more general coordinate-system
problem on the Print Preview page (see bug 1393494).

MozReview-Commit-ID: D4i2H8z5mtW
---
 toolkit/content/browser-content.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/toolkit/content/browser-content.js b/toolkit/content/browser-content.js
index f478618c1b5b0..ea830c8e8cdb7 100644
--- a/toolkit/content/browser-content.js
+++ b/toolkit/content/browser-content.js
@@ -139,6 +139,12 @@ var ClickEventHandler = {
     if (!this._scrollable)
       return;
 
+    // In some configurations like Print Preview, content.performance
+    // (which we use below) is null. Autoscrolling is broken in Print
+    // Preview anyways (see bug 1393494), so just don't start it at all.
+    if (!content.performance)
+      return;
+
     let domUtils = content.QueryInterface(Ci.nsIInterfaceRequestor)
                           .getInterface(Ci.nsIDOMWindowUtils);
     let scrollable = this._scrollable;