crostini: Add a feature flag for username picking.

Bug: chromium:914515
Test: CQ
Change-Id: Ibfacf91020b5bd80c905967accb24c438c0293b4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2006838
Commit-Queue: David Munro <[email protected]>
Commit-Queue: Julian Watson <[email protected]>
Auto-Submit: David Munro <[email protected]>
Reviewed-by: Julian Watson <[email protected]>
Cr-Commit-Position: refs/heads/master@{#732759}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index 46fa716..5d99429 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -2007,6 +2007,9 @@
 extern const char kCrostiniDiskResizingName[];
 extern const char kCrostiniDiskResizingDescription[];
 
+extern const char kCrostiniUsernameName[];
+extern const char kCrostiniUsernameDescription[];
+
 extern const char kCrostiniUseBusterImageName[];
 extern const char kCrostiniUseBusterImageDescription[];