Bug 1171029 - Only omit legacy scroll events on GTK3. r=karlt

--HG--
extra : rebase_source : c4badf1f606bbb5cf0052265f38514acc3eee63c

widget/gtk/nsWindow.cpp

@@ -3124,7 +3124,8 @@ nsWindow::OnScrollEvent(GdkEventScroll *aEvent)
         return;
 #if GTK_CHECK_VERSION(3,4,0)
     // check for duplicate legacy scroll event, see GNOME bug 726878
-    if (mLastScrollEventTime == aEvent->time)
+    if (aEvent->direction != GDK_SCROLL_SMOOTH &&
+        mLastScrollEventTime == aEvent->time)
         return; 
 #endif
     WidgetWheelEvent wheelEvent(true, NS_WHEEL_WHEEL, this);