[gnome-shell] SwipeScroll: Only allow starting with the left button

[Adel Gadllah <agadllah src gnome org>]

commit c450120409ebca2580d1c6383c1e5be54a6c6c08
Author: Adel Gadllah <adel gadllah gmail com>
Date:   Sat Apr 23 09:45:58 2011 +0200

    SwipeScroll: Only allow starting with the left button
    
    Currently we allow starting swipe-scroll with any mouse button
    which is weird from an UI pov and causes inconsistencies with
    event handling.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=647186

 js/ui/overview.js |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/js/ui/overview.js b/js/ui/overview.js
index 9d4cad8..ec67625 100644
--- a/js/ui/overview.js
+++ b/js/ui/overview.js
@@ -281,7 +281,8 @@ Overview.prototype = {
     },
 
     _onButtonPress: function(actor, event) {
-        if (this._scrollDirection == SwipeScrollDirection.NONE)
+        if (this._scrollDirection == SwipeScrollDirection.NONE
+            || event.get_button() != 1)
             return;
 
         let [stageX, stageY] = event.get_coords();