Bug 1974265 - Add "Turn on Vertical Tabs" option to titlebar spacers context menu. r=nsharpley,dao

Differential Revision: https://phabricator.services.mozilla.com/D267155

UltraBlame original commit: bf6143514327e3401252a92c65f6c05ce0be59f5

Author: marco-c

browser/components/customizableui/ToolbarContextMenu.sys.mjs

@@ -1553,6 +1553,23 @@ removeFromToolbar
 "
 )
 ;
+let
+isTitlebarSpacer
+=
+toolbarItem
+?
+.
+classList
+.
+contains
+(
+"
+titlebar
+-
+spacer
+"
+)
+;
 /
 /
 Show
@@ -1645,6 +1662,9 @@ localName
 "
 toolbarspring
 "
+|
+|
+isTitlebarSpacer
 ;
 let
 toggleVerticalTabsItem
@@ -1843,6 +1863,9 @@ localName
 "
 toolbarspring
 "
+|
+|
+isTitlebarSpacer
 ;
 /
 /