[Tab Groups Collapse] Add no policy tab freezing behind a flag.

Bug: 1110108
Change-Id: Ie23896b56983ec165180e4f02deddce7bdd9d735
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2321530
Commit-Queue: Charlene Yan <[email protected]>
Reviewed-by: Connie Wan <[email protected]>
Reviewed-by: Peter Boström <[email protected]>
Cr-Commit-Position: refs/heads/master@{#792344}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index c2a94f1..683174da 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2191,6 +2191,10 @@
     "Allows a tab group to be collapsible and expandable, if tab groups are "
     "enabled.";
 
+const char kTabGroupsCollapseFreezingName[] = "Tab Groups Collapse Freezing";
+const char kTabGroupsCollapseFreezingDescription[] =
+    "Experimental tab freezing upon collapsing a tab group.";
+
 const char kTabGroupsFeedbackName[] = "Tab Groups Feedback";
 const char kTabGroupsFeedbackDescription[] =
     "Enables the feedback app to appear in the tab group editor bubble, if tab "