From bd3dba7dd8419efe34c17bff8caf68163a107419 Mon Sep 17 00:00:00 2001
From: Jared Wein <jwein@mozilla.com>
Date: Mon, 10 Apr 2017 16:45:33 -0400
Subject: [PATCH] Bug 1355211 - Scroll events should be prevented in all cases
 except when allowunderflowscroll is true and the scrollbar is hidden.
 r=enndeakin+6102

MozReview-Commit-ID: GXhf9bM6ZIo

--HG--
extra : rebase_source : 6599f20293c793a1dc10c4fce5467386cda878c8
---
 toolkit/content/widgets/tree.xml | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/toolkit/content/widgets/tree.xml b/toolkit/content/widgets/tree.xml
index 2d2ca7c1667a..20e31cb0fd8b 100644
--- a/toolkit/content/widgets/tree.xml
+++ b/toolkit/content/widgets/tree.xml
@@ -719,15 +719,15 @@
       </handler>
       <handler event="MozMousePixelScroll">
         <![CDATA[
-          if (this.getAttribute("allowunderflowscroll") != "true" &&
-              this.getAttribute("hidevscroll") != "true")
+          if (!(this.getAttribute("allowunderflowscroll") == "true" &&
+                this.getAttribute("hidevscroll") == "true"))
             event.preventDefault();
         ]]>
       </handler>
       <handler event="DOMMouseScroll">
         <![CDATA[
-          if (this.getAttribute("allowunderflowscroll") != "true" &&
-              this.getAttribute("hidevscroll") != "true")
+          if (!(this.getAttribute("allowunderflowscroll") == "true" &&
+                this.getAttribute("hidevscroll") == "true"))
             event.preventDefault();
 
           if (this._editingColumn)