desktop-share-menu: add chrome://flags entry

This allows for testing the feature :)

Bug: 1218211
Change-Id: I02110e0bd916bfb6d00c479c6861cde9c90a7ac5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3163133
Commit-Queue: Elly Fong-Jones <[email protected]>
Reviewed-by: Kristi Park <[email protected]>
Cr-Commit-Position: refs/heads/main@{#921901}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index dd5dfc03..1437c9e 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -2842,6 +2842,11 @@
     "Enables users to justify their extension requests by causing a text field "
     "to appear on the extension request dialog.";
 
+const char kShareContextMenuName[] = "Share context menu";
+const char kShareContextMenuDescription[] =
+    "Whether the sharing options in various context menus are grouped into "
+    "a common submenu.";
+
 // Android ---------------------------------------------------------------------
 
 #if defined(OS_ANDROID)